Bass amp for a tri-amped system?

I have a speaker-required active crossover which feeds the mid/highs to 2, fet input/tube output 200 watt mono amps and the low frequencies to a Belles 350 stereo amp. I'm interested in tightening up the bass a bit and wondering if there is an older amp out there that might replace the Belles. I know the Krells have always had good grip on the bass, but wondering if there is anything else out there. Should I be thinking of any issues? Compatibility?
Thanks for your comment. I've had several high-end audiophiles (including a reviewer for DAGOGO) and musicians listen to my set-up.
And I think, again as a result of the outboard active crossover, a lack of coherence has not been an issue. In fact, I've received unanimous compliments.
I'm also fortunate to hear some 6 figure systems and where my humble rig consistently suffers is ultimate articulate, resolving bass. (And maybe my speakers are just not capable).
What I mean by "dynamic resolution", compared to those high buck rigs, mine is a bit sloppy at the lowest of frequencies. Upper bass, lower mids have actually very good resonance and articulation.
As to cabling, I've reworked my entire system with Stealth Indra, Metacarbon, Nanofiber and Air King. The Air Kings are solid silver and I have them connected to the Belles. No comprise there - they are really stunningly transparent.
So short of reconfiguring speakers and amps, which someday, I know I will have to do, my short-term fix/mod might be the bass amp - at least that's what I'm considering. I have no reference for comparison.
And you may be right that I'm chasing a tweak that cannot be enhanced. However, ultimately your advice is sound. thank you.
Just one more note. I've been addressing this issue for about 15 years in this room. I've placed Bass Busters in all four corners along with very careful speaker placement. (Vandersteen, Tannoy, Martin Logan and now Signature- 5 yrs). Amplification has been ARC, B&W, BAT, and now Signature. It could be just the nature of the room which I know will not change.
And with all the upgrades I've made in the last couple of years - the entire front end sources, all cables- interconnects and power. The system has taken several fantastic steps to where maybe the ultimate next step is probably speakers. But that will be for another decade.
I'm totally unfamiliar with Eagles. I took the liberty to see them on your virtual system. They look interesting. I'm using 200 watt monos which these mammoth speakers need to sing. I'm actually completely content with my Signature amps - they are really quite wonderfull. The best of both solid state and tubes. Thanks for the suggestion.
IME, you can definitely optimize certain aspects with various amps that address a particular range better.

But in the long run, after you've gotten used to the sonic effects of that combo, the more cohesive and musically compelling sound from matching amps outweighs the "audio excellence" of disparate amps with disparate dynamics, tone, phase response, etc.

So the job of discovering the best amp that will work at all frequencies is much more difficult.

About the only time I've had luck mixing & matching was with subs working from 40 Hz or lower.

Please forgive me, but I don't understand the "disparate" problem if the active crossover prevents frequency overlap. and once again, it is the lowest of frequencies I'm trying to address probably below 40 Hz. Getting "used to it" doesn't explain the evaluations performed by qualified audiophile visitors. Once again, I think I understand the reality of mixing amps, it's well documented. however, I believe in this case, it minimally applies.
I've heard setups both ways. I think with a passive crossover, using the same amps makes sense and in my experience sounds better. With an active crossover it will sort of blend the two or three amps sound's together so there may be less sonic differences in the end and should sound like one voice. I would make sure to use all the same cabling either way I think. Your system looks and I'll bet sounds awesome. My speakers, Legacy Helix, are quadruple amped using a Xilica digital crossover and are supplied with about 3,600 watts per channel. Talk about headroom!
You might want to check out my system as well.