Rotel RA-1592 MK II or something else to deliver around 200W to B&W towers around $3000?

There are a couple of early 90's solid state McIntosh power amps listed for prices that I could stomach.  There is an MC7150 for $1650.  There is an MC7200 for $2200.

Thoughts on these?

Lots of good options out there.

As much as I like their amps, I think McIntosh are over priced and capitalize on legacy reputation and aesthetics. But if $ is no (significant) object, then I may have them in my system too.

While not inexpensive, I have grown very fond of Plinius products … so much that I repurchased an 8200MkII integrated and sent off to be completely refreshed. This one in particular seems to combine the strengths of tubes and SS while mitigating each ones downsides. This one will never leave again. And well within your budget. Also a used Hautonga would fit. I think the sound is just a bit more clinical than the 8200, but offers the convenience of more remote control functions.

One says Bryston is mellow, it's accurate. Some amps are bright to give the appearance of better high frequency response, listen closely.

 @yukispier

I currently have the B&Ws but nothing else.

Budget is still hovering around 3K... but it could be expanded in the next few weeks

So you need at minimum these components:
1) Preamp
2) Amp
3) Streamer
4) DAC
5) Cabling
6) Audio rack?
the 3K is not much to work with.

....I’m more sold on building a better system with separates for the same price.

I think you have this backwards.  While separates perform better than integrates, integrates have significant cost savings by reduction in casework and cabling though at the expense of a little performance - it's a tradeoff.  For the best price/performance, integrates are the better value especially if you are on a limited budget.

... putting most of the budget into a very good power amp and getting a pre & dac that will be OK for now but upgrading those components in the next year or so.

In high-end audio, the each component in the entire audio chain matters.  If you attached a quality amp to mediocre upstream components you'll get mediocre sound.

A better solution would be to build a system you can enjoy now but with the flexibility for future changes/upgrades.  

I like the Elac Alchemy:
*2.5k DDP-2 Preamplifier/DAC/Streaming End-Point and maybe the
*1.5k DPA-2 Stereo/Mono Amplifier
designed by Peter Madnick of Constellation Audio fame.  Plenty of positive Audio Alchemy reviews and this next generation should be better.  You can save more by buying used, and you can upgrade individual components later.  

There are a couple of early 90's solid state McIntosh power amps l

The technology for high-end audio is constantly progressing so generally speaking performance today is better than what has come before.  This includes the sonics of amplifiers.  Trying to save $ by buying vintage usually comes with a significant reduction in sound quality vs newer designs for the same $.  When buying vintage electronics, make sure you know what you are getting vs other alternatives.