: What equipment do you have now?
My experience has been mixed on whether a tube preamp or power amp gets you "that tube sound"; I think it depends on the components and system. I used to recommend a tube preamp with a SS amp but that did not always work, especially with some of the better (lower distortion) tube preamps. That said, if you pick up one of the current crop of tube preamps or hybrid units (e.g. Luxman etc.) you could try it out.
My advice would be to look for used gear if you want to try tubes to see if you like them or not. I love the sound, but it is not usually (as) accurate, and too often I found tube amps just didn't provide good bass and HF sound (midrange was gorgeous). And that was with Maggies, which provide a pretty flat load over frequency; with conventional speakers, and IME, mating a tube amp to the speaker is very much an iterative personal journey to find the match you like. I also got tired of fussing with tube replacements, and my old ARC preamp liked to destroy its power supply about once every year or two, so I have not pulled out the preamp (SP3a1) in ages (need to sell it) and sold my ARC power amp (D79) a few years ago. Years ago I had Magnepan MG-IIIa's (in storage now) and used the D79 on the mid/tweeter panels with a Counterpoint SA-2220 hybrid (tube input, MOSFET output) amp on the bass. I used a DIY passive crossover (wired into the preamp) for the Maggies, and a DIY active control box (rossover + servo) for the (DIY) subwoofer. Awesome system, not as accurate as my current one, but lovely sound. As last set up I used a dbx analog crossover between Maggies and subs with a single power amp (SS or tube) driving the Maggies.
Ultimately I decided I wanted more accurate sound, with tighter bass and better extreme highs (which I can no longer hear, alas), got tired of the fussing with tubes and crossovers to set up multi-amped systems, and went with a single big SS amp and subs using my AVR for bass management. Doing the same now I've switched to Revels (which are a more demanding load than my Maggies). Dynamics and bass are just better with the SS amp (as evidenced by my measurements and ears, don't really care what the rest of you think
If you have subs now, I would keep them, and add a line-level crossover after the preamp. That is what I did for decades, using everything from passive DIY designs (Marchand makes nice passive and active crossovers albeit a bit pricey) to active analog (e.g. an old ARC tube crossover, inexpensive dbx 223, etc.) to DSP-based filters.
I couldn't say which is best for you. Keeping the subs should help the bass, so I would do that, though IME a tube amp will not provide as tight of midbass. A SS preamp and crossover (whether part of the preamp or not) with a decent used tube power amp on the Revels might work. Hopefully you could sell the amp without too much loss and pick up a SS amp if you didn't like it. Alternatively, pick up a used tube preamp with SS crossover and power amp and see how it sounds; that may be a cheaper choice, but may not be as "tube-y" as using a tube power amp. My favorite place for tubes was in the phono input stage since they didn't clip the way SS phono preamps always seemed to (with a few rare exceptions). Going with new components is always nice but makes for an expensive trial. In the 70's and 80's there was a lot of Dynaco and other tube gear around in good working order; not sure what's available today.
Rex likely has more and more recent experience.
FWIWFM - Don