Thank you all for the responses and especially for the link to the google doc. It gave me a lot to think about. Tom's point hits a little close to home ("fullness, richness, lushness, warmth"). The pursuit of such "ideals" has led me to consider B.A.T. and PS Audio for their promised "tube input stage". But is distortion really the goal? And how do I know I'm getting the "right distortion", haha.
The consistent message I've seen is that Thiels (including my OG 2.3s) like current, so I've been looking in the 400+ wpc @ 4 ohms range. But the rears (OG PowerPoints), while still rated @ 4 ohm, have recommended specs more in the 100 wpc range.
So maybe the most cost-effective (but kludgy and/or boring) option for me is to replace my pre-pro with a good AV receiver (Looking at Denon, possibly Anthem), use the onboard amps for the rears and possibly height channels in the future, and then just use the three still-working Krell amps from my old Home Theater Standard as the front three.