I moved to that kind of setup a few years back now and found a Synq1K0 which is a 1U shallow rack unit and ratings below.
Audio : max. output channels2
Audio : Wrms 4Ω stereo, per channel 540
Audio : Wrms 8Ω stereo, per channel 300
Audio : Wrms 8Ω bridge 1080
I have tried bridge mode a couple of times but usually have it in mono mode or stereo using only one channel.
The noise floor in my setup is really low and i generally have the power amp on or close to full and the pre-amp and bass levels to suit. Seems to give me a bigger fuller sound.
I also have a crown xls1502 which again is a shallow rack but 2U, and like the OP i use a Big Twin II as my main cab.