Best improvement for the buck

I just recently sold a McIntosh mc250 and now have about $900 to spend to improve my system. 
Parasound p5 
Parasound A21 +
Denon dp51f  with grado gold
Magnapan 1.7i 
Klipsch 10" sub on stand
Oppo bdp83 
Blue Jean interconnects 
Sony 8" sub on stand
Monoprice xlp interconnects 
DIY braided speaker cable. 
So now the question is what is the most logical improvement or improvements.any suggestions?
Why did you sell the MC250?  If you are spending just the 900, you can’t get the Parasound A21+.  That is a new amp that sells for $3000.00.  What was it about the MC250 you did not like?  What is the rest of your system?
Depending on who you ask the correct answer is "room treatments" or "sell all your gear and buy a Raven integrated and a pair of Tektons". 
If you are keeping your system as is, take a look at ADD-POWR

have about $900 to spend to improve my system

When I was young, I'd place a penny on the head shell when it went over a skip on the record..... really!
Depending on who you ask the correct answer is "room treatments" or "sell all your gear and buy a Raven integrated and a pair of Tektons".

Don't be silly. Depending on who you ask the correct answer is "GIK" and "How NOT to buy a subwoofer" or something that actually makes sense.

Although I must admit a Raven would be a vast improvement.

Well actually I'm looking at all Raven cables which would wipe out my stash but might be a game changer.

My apologies, I thought that was what you were considering buying.
Your room, or your DAC/pre.

If your sources are limited, I'd get a Mytek Brooklyn + which has a built in phono.
@audiomaze ...

If your looking for quality cables at a reasonable price, give Grover a call. I've heard his latest cables at the homes of friends and found them to be impressive.

Consider upgrading your speaker cables. I would advise trying the Alpha Core Goertz MI 3 Divinity Bi-Wire. Goertz has had a known synergy with Magnepan. The Cable Company has a 30 day return policy. A stand alone tube phono preamp like an Allnic H 1200(own one) would bring your viinyl to another level. I do agree room treatments are a must but IMO have your system dialed in then the room treatments should be more effective.
I'm with @erik_squires  -- especially about the chance to improve the DAC in that Parasound P5. You have a lot of nice options at $900.
You could explore variety in obtaining a second, different type of speaker to have a contrast. It's a great way to play the game.  

Obviously, you can upgrade your sound with the speakers you have, or new ones, but as an option to hear more variety, a second speaker, such as a horn hybrid, is a terrifically fun way to go. Imo, there are not many things in the hobby more fun than swapping out a speaker and having a "new" rig, a new sound at your whim.  :) 
I would start with your amp/preamp combo and go from there. Move to source improvements afterward.


IMO a mediocre horn speaker at $900 new or used would not improve his system, since that is what the OP is after.. A properly set up Magnepan 1.7i rivals box speakers costing ??? you know the rest!
The point of variety is variety. 
Horn speaker was an example. 
Maggie's are all that to some. To others like myself they are just a flavor.
I had the P5, it’s no match for the A21+. The P6 doesn’t seem like a huge improvement, though a bunch of minor improvements could be worthwhile

Whatever preamp you chose, make sure it is True Balanced and connect the amp/pre with high quality XLR cable: I use WireWorld

It looks like the cable upgrade seems to be the way to go. At least a start.  Thank you all. 
People who keep changing their cables do so mainly because they never fix the underlying issues with their system, poor acoustics, poor speakers, poor speaker interaction with their room, the rare but not unheard of poor interaction between amp and speaker .... cables, unless there is something truly wrong with them, are so far down the list, it is laughable, and it is mainly the cable cult that pushes them, no matter what. For some people, every problem can be solved with a hammer.

I am a fan of Magnepan, especially if you have an untreated room. It is why they win "best" of show so much. I don't think it is because they are so obviously better than other speakers in a properly setup room, but that they work well without treatments giving them a serious edge in those situations.

Even with the Magnepan, room treatments will still help. The are less immune to floor/ceiling effects, but still need wall treatments for optimum performance, and then bass, which brings us to your subs, which don't sound too hot. Better subs, and perhaps better bass management from and equipment standpoint, are the next step up, and if done in conjunction with some basic room treatment, is going to make a difference so far beyond what any cable would ever do that it is almost laughable discussing them.

Most Magnepan users are pretty set on their speakers, but if you are willing to invest in a "room", and $900 is not going to do it, but I personally believe that the combination of flatter frequency response, even in room, and lower distortion of a good dynamic speaker can result in better sound than your 1.7i, but I will certainly give credit to the "sound" of a planer array may not give something you give up easily.
"When I was young, I'd place a penny on the head shell when it went over a skip on the record..... really!"
I did the same except it was not a penny. As time wore the record out, and time is money and vice versa, I started putting bigger coins to accomodate bigger and bigger skips.

The difference from then is that I am still young, if not younger.

I can't comment on the swarm which is a specific model of bass array, but conceptually bass arrays are much easier to integrate into most listening rooms versus, well almost anything else. If you have the money and space, you can use room treatment, but doing it right, it not easy, and taming deep bass requires large structures or good/lucky use of harmonic traps.  If you have a lot of flexibility in placement, very good results are possible with 2, but 4 is going to allow more flexible placement. Careful with subs near mains. If the swarm has reasonable bass management and they are low distortion so you don't get false images, then I would expect they will work well.
Those Blue Jean interconnects will throttle anything you put through them. I speak from experience.
Basically yes. I really tried to like them. However they are opaque and caused a loss of information and dynamics. I found them to be a false economy and was relieved when I moved on.

Having said that, as I do not want to hijack this thread and turn it into a yet another dead end cables war, I will post no responses to any ensuing posts on the matter, period.