Monoblocks I've known & loved:
VTL Compact 100s (sound heavenly, but reliability may vary)
Quicksilvers (sound more to the solid-state end than the tube side)
Emotiva XPA-1s (I liked the Gen. 2s best)
Bob Latino M125s (but get the KT88s, not the 6550 power tubes for sure, and maybe the tube rectifier also)
Heathkit 12 wpc DIYs (they may not be flat, they may not be powerful, but WOW!)
Dynakit Mark IIIs (only 60 wpc but a MIGHTY 60 watts!)
Monoblocks that didn't impress me:
Emotiva XPA-1Ls (sound didn't click and reliability may vary)
Any stereo amp bridged to mono (don't blow against the wind here - really...)
There are probably more that I've forgotten, but off the top of my head...
Boomzilla