Thanks Autre, that helps a lot.
I have owned both Adcom and Rotel(RC-990/RB-980BX) pre/power combos. As great a value as both are, they can be hard, edgey, and dry as all getout. Moving to tubes will be a revelation. I'd suggest selling your Adcom preamp and use the extra dollars to get a better tube integrated, it will proably degrade overall performance.
The Revels at 87dB would probably benefit from 20-40 wpc of push-pull amplification, depending on your musical tastes and volume levels.
Buy used to maximize your purchasing power and look for Jolida(Jolida JD-302B), Antique Sound Labs (AQ-1003 DT, AQ 1001 DT), and Consonance Opera( M99 Plus, M100 plus) integrated amps.
All three of those manufacturers have a good history and reputation for low-priced tube gear.