I own the below system and I am looking for an improvement by upgrading one of the components (budget $2000-3000).

-Graham Audio LS5/8 (large BBC studio monitor speakers)
-Analysis Plus Oval 9 speaker cables
-Mark Levinson ML 23.5 power amp (completely recapped by Madrigal technician)
-Audio Research LS 5 MKII preamp (restored and new tubes)
-VPI Prime turntable with -Dynavector 20x2 H cartridge
-Parasound JC3+ phonostage

Quite standard power cords and interconnects, no power conditioner.

What change would make a significant difference? Larger soundstage, more liquid, open sound without loosing the dynamic punch?

Thank you for your time and I would appreciate any ideas.
Room, speaker positioning and consider subs. The gear looks competent to me.

After those two factors, the tweaky cable/doodads. You could go beyond that with a PC and the latest software too, if you don’t trust your ears.

Maybe before the other stuff, clean power from the outlet if you don’t have decent service to start with.

Forget it and enjoy the music, if the system is in a living space like most listeners.

Go full analog with tubes and a table. That’s my excuse for not having a room. Just obsess on finding the BEST cheap record of amazing music.

Ceiling panels for damping made a HUGE impact in my very "hot" living room.(wood/windows everywhere)

Aesthetics are paramount in my case. YMMV like the rest of the madness.

Edit: I meant to add my system is in a living space, but I'm able to get the speakers in the room(5ft) and away from the sides(3ft) Subs take care of low end duties.
That budget would get you a set of Synergistic Research Element CTS speaker cables that will do exactly what you want - larger sound stage, more liquid and open- and with much greater dynamic punch. You could probably afford to have Michael Spallone upgrade their power supplies for truly jaw dropping performance. The main downside being when you hear just how much difference quality cables can make you will be spending a lot more money on them in the future.  

https://systems.audiogon.com/systems/8367 (These have the Michael Spallone power supply mods) 

Or you could add a full room treatment of Synergistic HFT, both room and speaker kits, not as staggeringly huge as the CTS cables but close. 

But if it really is a deep wide dynamic liquid sound stage you are going for then ditch the ML and get a Raven integrated. You could probably sell the ML and AR for enough to get within $3k of a Raven Reflection MkII integrated, which will be an even more staggering improvement than any of the above ideas. Which is really saying something. https://www.ravenaudio.com/product/reflection-mk2/ 
Those seem like really nice speakers but they bottom out at 40. [from website: 40Hz to 16kHz, ±3dB]

I have some speakers now that go down to 38 hz but the presence of just one REL sub does quite a lot, very noticeable, for the entire spectrum. I got that $1900 sub used for $900 and I am pretty convinced that a second sub is necessary. (Just waiting for a bit to see how some other things develop.)

Perhaps get a sub or two as a tryout and see what happens?
I agree with the other folks here who mentioned a sub.  I would look at adding a very refined, sealed sub.  JL or REL make outstanding subs.  

This will help deliver a bigger sound stage on a lot of tracks as you will improve accuracy and frequency response below 50hz.  

The other option would be to look at a nicer cartridge.  Especially with that JC3+, something like an Ortofon Cadenza Bronze could be interesting as it will add a bit of sweetness to the overall sound profile.  I run a tube phono stage and have all tube gear so I run the more detail oriented Cadenza Blue as the Bronze would just be too much.  

I am an Ortofon dealer. PM me if you are interested.  
Room, speaker positioning and consider subs. The gear looks competent to me.


Room--acoustic treatment, pull the speakers out further (soundstage), but then you lose some base (consider 2 subs).  As a fourth choice, some Triode Wire Labs Spirit Mk II interconnects.

Thank you for all the suggestions! 
I have a decent Canton subwoofer in my home cinema set-up which I can try In the audio system. 

I didn’t mention that my speakers are positioned 6ft away from the back and side walls. And I have a DIY bamboo butcher block with isolation spikes under the VPI turntable, but I don’t consider installing any sound panels due to aesthetic reasons.

Amp wise, is there anything else out there in the $8000 range which beats the ML 23.5 + ARC LS-5 combo, besides that Raven integrated millercarbon suggested? The amp are the weakest (certainly oldest) link I guess?

anything else out there in the $8000 range

@bms72 You’ll need to figure out what beats what...

Take a look at High Current amps. They will control (grip) your Graham Audio LS5/8 better and result in (I believe) better outcomes.

T+A comes to mind for a high current solid state option. Though not often listed, the PA 3000 HV integrated can be found used, close to your listed budget. Given the Graham’s ’signature’ it would offer a balanced pairing.

There is a MasterSound Evolution 845 integrated listed on usaudiomart for 10K. That (in my estimation) might be a terrific tubed option.

Note: these are options I’d consider with your speakers. Not knowing your preferences...well you know....
If you have zero aftermarket cables, that would be where I'd start for the biggest bang for the buck.  Having just been through a sincere upgrade  in cables about 5 years ago, it began with the Darwin Silver IC's.  I'd had several good for the money cables like Morrow, Crimson, DNM, Audioquest, Magnan, that were all nice sounding cables and a noticeable upgrade from standard cables, but the Darwin's opened my ears as to what was possible at a similar price.  Their cables got progressively more expensive the past couple years, but were also better sounding as they came out with new cables that were more expensive.  BUT...the Darwin Silver would get you much closer to what you want at a very reasonable price--under $175 per IC pair.  It would leave you with enough to buy a couple nice power cables and maybe even some good speaker cables.  You could find some used WyWires Juice II PCs for under $250 per.  If the speakers you have are what you really like short of their dynamics and low bass, the sub would be a good idea.  If you did the ICs I mention, added a power cord or 2, and got a nice sub, you'd think you'd died and gone to heaven compared to what you have now.  Other than speakers that don't do low and a total lack of good cables, your system is a nice collection of components.  The cabling would be the single biggest change you could make.

The components in my system have remained relatively unchanged for the last 4-5 years, but I've upgraded most of my cables in all categories considerably again.  I've also done much tweaking to almost all areas mostly with great results.  This has been done with both analog and digital.  

PM me for more detailed info.

Raven Audio is awesome and I have the CeLest towers and use all Raven Cables, power, speaker and interconnects, top shelf gear for a reasonable price.

I am a Simaudio guy and have the Moon 390 pre and 330A power amp. Just awesome gear and a big wide liquid sound stage. 

Though I am going to give the Raven Blackhawk a shot in a smaller system in my house, with their 45 day return policy why not?
Instead of buying one expensive sub, You might want to consider a DBA swarm.  AudioKinesis has a well-regarded all-in-one "kit" for $3200, or you can DIY from separates.   http://www.audiokinesis.com/the-swarm-subwoofer-system-1.html
Single most noticeable ositive change I ever experienced was when I first put in aftermarket mains cables for the stockers. I use Triode Wire Labs. 
Rogue RP7 with a Musical Fidelity M6s PRX.  For new gear, on your budget I think that would be pretty fabulous.  
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As your current system seems well done I will assume your acoustic treatments are also well done.

I tend to think I'd sell the older ML amp and shop for a 6-12 month
old, one owner Pass Labs XA25. Can be had for $3k.

That will give you the low end slam you want as well as better
overall experience. 

You already have the tube preamp so good synergy with SS Class A

My 2 cents worth.

Please keep us posted on your results.
Isolators under your ARC, I have Nimbus under my REF5se...

arrange to borrow an HRS Turntable platform
Thank you all!!
I will try different power cords, IC’s and isolators first, before changing any of the other components. Thanks again for all your suggestions
bms72, sorry that I am late to the game. You have a nice system. Power cords and isolators are not going to do much. But what will make a significant difference is a new tonearm. I believe you have a unipivot arm on that turntable. Unipivot arms have to many degrees of freedom, they are floppy and hard to keep perfectly aligned. Several cartridge manufacturers such as Lyra recommend against using them. They are particularly bad with medium to low compliance moving coil cartridges such as yours. Moving to an arm with fixed bearings will for certain improve bass and dynamics and may well improve other areas. Look at Origin Live, Kuzma, Reed and many others. VPI also now makes an arm with gimbal  pivots which might be a direct replacement. 
Thanks mijostin. I am certainly not an expert when it comes to tonarms... but I m actually pretty satisfied with the bass and dynamics in my system. My current MC cartridge is a Dynavector 20x2H (high output). 

I am looking for a larger more open soundstage, more liquid, but without loosing the punch. The ML 23.5 does pretty well with my Graham speakers, even though they only go down to 40hz. 
You have gotten alot of different opinions but this is where I would start.  First play with the placement of your speakers.  Sometimes if you find the perfect spot in your room the soundstage will open up and your speakers will deliver what you are looking for.  Next I would look at the platform you have your turntable on.  I have a top notch table but it really improved with a 3" maple platform underneath it.  Cost about $300.

Look at a $1,500 - $2,000 lomc.  That along with better vibration management of your VPI will maximize your front end and possibly astonish you.  

I know nothing about your cables but the attention to your source is where I would start.  

My experience was jaw dropping when I added a high quality platform system for my turntable.  The definition of bass, particularly on musical passages that had repetitive kick-drum beats, was a revelation.  Anything with impact became so much more well defined and audible.  My soundstage and imaging was always very good.  But with the new platform system it all became even wider and deeper.  I chose the Symposium Acoustics Segue ISO Platform combined with the Rollerblock Jr. and the upgraded balls of tungsten carbide.  While that type of upgrade may not be what you are seeking at this moment, trust, at some point if you make that upgrade to your system you will be amazed at the experience and very happy with the investment.  By that time I had already made numerous cable upgrades for signal and AC.  Each and every one of those upgrades made a difference so I do recommend doing so.  Adding the Segue ISO with the RBJRs was like having made an entirely new component upgrade to the system, and for a fraction of the price.  Retail is $550 to $650 for that setup, depending on which size of platform that your turntable would require.

Enjoy the fun.
Dear @bms72 : Try the Analysis Plus Silver Oval speaker and IC cables, those are the ones I'm using in my system.

I owned your 23.5 and even today very good amp and competitive with today designs.

The unipivoth VPI change advise is a must to do it due that all unipivots tonearm designs are way unstable and develops higher levels of distortions and can't fulfill the cartridge needs, you need a gimball/fix bearing tonearm design and when you do it you will attest the wide differences for the better against your unipivot with your Dynavector cartridge.
Latter on you can change your HO Dyna for a LOMC Dyna model, your phono stage has enough clean gain to do it.

Regards and enjoy the MUSIC NOT DISTORTIONS,
Which XLR cabel will be perfect to connect 390 with 330a?
Any power cable for 390?

thanks a lot