Tube amps under $7500

definitely not expert in this area, but four different thoughts:  (1) some tube amps come with gain adjusters.  (2) if two amps have same gain, no issue.  (3) if different gain, you can lower gain on higher gain amp thru use of resistor on interconnect. (4) use an external passive preamp (attenuator) for the higher gain amp (For example, Lab12 sells one for $750.)  Again, just brainstorming with you, am sure others know much more about this, but if it works, you could save a bunch by getting a relatively cheap class d amp for lower end, and then you can splurge on a relatively low power tube amp for tonality at the high end.

I suppose it is a given that no tube amp in my price range can match its SS equivalent on bass

I think that would only be true if your preference is strictly solid state for bass.  I had a tube amp that sounded great, but with steroetypical bass disadvantages.  My 24 WPC Air Tight has great bass control and plays very loud for my room and even with some previous 89 dB speakers.  For me many of the SS I would compare it to would play louder and have some more dynamic headroom that I don't need,  but would not sound as natural.  I think it comes down to what sound signature you're looking for and musical taste preferences to get the best match with you and your speakers, not necessarily a certain type of amp is "the best" at this or that.  You can go down a rabbit hole just in what is the best class D amp or if/ when is it better than A or A/B as far as what's best just for SS bass.

"You can go down a rabbit hole just in what is the best class D amp or if/ when is it better than A or A/B as far as what's best just for SS bass."
@yoder  Wish I knew the trick for highlighting text copied and pasted . . . anyone?)

I was one of those who suckered on Bob Carver's intro product as his own company: a megawatt Bang For Buck Class D stereo amp, perfect for quick money exploiting the hormonal market of the time. Thought this would power the Maggies I was using back then. Um, no. So much for Class D. Sure, it's better 40 years later, but I'm A-A/B all the way now when it comes to SS power.
As for sonic preference in bass presentation: realism is essential, but so is amplitude, and that sense of dynamic headroom still thrills me. Guess you could call me a bassoholic -- my ancient ears gravitate to the bottom frequencies because they're the only ones I can still hear in a "critical listening" way. That's why Legacy, and you're right, that's why SS for the bass, providing it's 5-10 watts of Class A with A/B beyond. 
Given that I'm never spending $30k+ for a Fortress tube amp, we're down to feasible bi-amping. At least I still hear well enough above 400 Hz that the tube glow might be magical and worth implementing if not too fussy.
 

Alot of good suggestions here....BUT....the one I think gives you a sound of Real Music beyond the speakers themselves is the LAB 12 Integra 4....highly recommended. Good luck in your search...There's lots out there. I  also second Audia Flight.

If you have not reached out to Aric at Aric Audio, then your due diligence is not complete.