What would you do?

The speaker amp synergy is pretty important, so if your current amp and speakers are a great match, I'd opt for a tube preamp if I could only pick one.  (but being a tube believer, I gotta suggest both! 😎)

@knotscott 

Agreed on speaker + amp synergy.  Since I currently use an integrated, I could try a preamp since my Accuphase allows preamplifier and power amplifier sections to be used separately. 

Preamp. The preamp is the heart and central component. That is where to start. A good tubed preamp will be very musical and reliable, and give you a taste for what is to come if you continue down the path. 
 

BTW, for the first twenty years in audio all of my equipment was solid state and then over the following thirty years one component after another got switched to tube equipment (my system is shown under my ID). My only regret was no doing it much faster.

Back when I was figuring this out as I was building my system I experienced the most tube sound benefits from the power amp. Every tube piece made an improvement in sound, but for me the amp made the biggest difference. 

Lots of fun...I've done it with tube CD Player/DAC and Preamp...didn't want to deal with tubes in high powered amp, though with your speakers...

Definitely Tube Preamp

I only recommend what I have owned, this Vintage McIntosh mx110z Tube Tuner/Preamp is the best one I ever owned. If something happened, I would get another one without considering anything else.

here's one, no wood case like mine. You can find them with wood cases, or find a wood case separately later, they pop up frequently.

This convinced me to get one, glad I did

https://positive-feedback.com/Issue77/vintage_mcintosh_experience.htm#:~:text=The%20MX110Z%20makes%20vinyl%20%26%20FM,modern%20preamplifier%20on%20Planet%20Earth.

After a year, I took it to audio classics, they replaced a few resistors, and the best improvement: they replaced all the rca jacks with new gold plated ones.

..........................................................

It is FULL Featured, has two MM Phono Inputs, tape loop ....

http://www.berners.ch/McIntosh/en/MX110.htm

I get remote volume/mute from my Integrated Amp.

Get a nice tube preamp. I like tube power amps, but also love gobs of power (even on those 96dB Tannoys), and it costs a LOT more to get there with tubes (like my VAC Master 300's). And after all these years, I have to admit Tannoys do great with either tube or SS power - they're truly ambidextrous. You might need to shut off the supertweeters for SS amps though - ouch! And the pre/power equation absolutely might flip if you're a low volume listener - I'm not 😅

Tube DAC - tubes are just an extra thing in the way, and I'd just let the DAC do its thing without a superfluous tube buffer. I suppose I'd have to hear a Lampizator to be properly qualified to an opinion here, but I've never invested enough in digital to go there.

I really love my current system and there is nothing lacking as E-650 offers a very sublime listening experience.

If this is true, then do nothing.

+1 tube preamp

Another option is to insert the Modwright Analog Bridge here

I just bought a modest tube pre-amp , and even a modest one can impact positively...

Appreciate everyone’s advice so far, favoring Pre-Amp. No doubt, a good preamp is a heart of any great system. 

I agree with the majority in that a tube preamp is the way to go. Even when I had good solid state amps the first time I tried a good preamp I was hooked. 

@lwin 

Thanks, despite of majority votes for preamp; I am looking into both preamp and amp options. It will take a pretty special component to de-throne E-650. 

I believe the bigger challenge is finding a component that renders the music in a balanced way, without focusing on any specific sound orientation. Some of the high-end audio gear pinpoint particular attributes and highlight only a portion of something special. 

In my own system, I've got tube line stage and phono preamps, and solid-state power amp; that works well for me.... 

Integrated tube amp. With both preamp and amp- tube driven. To me, this is the only way to get tube sound. The other option, more expensive, is a tube amp and matching tube pre amp.

Given the request, replacing one of the 3 SS devices, I with those that recommend a tube preamp to start.  A tube amplifier may follow. 

I started that way and now have both a tube and a SS amp (in rotation)  in one system, and a tube/SS integrated in another one.

I also agree a tubed preamp and a good one can be a system changing thing.

I put a Backert Labs Rhythm 1.3 preamp in my system and was amazed at the difference it made in my bass. Much tighter. I am using a solid state McIntosh MC-462 amp.

Thank you all for your feedback. I am considering auditioning SW1X PRE IV Line Pre-Amplifier in my system.