I went through a BAT VK-31SE, Threshold T2, Mark Levinson 38S, Krell KRC-HR, VAC Renaissance Mk II, Conrad Johnson Premier 16LS mk II and a BAT VK-50SE while I owned my pair of Clayton Audio M-100's. Of all these preamps, I preffered the BAT's. The 31SE was a bit more dynamic and powerful, the 50SE was a bit warmer and fuller.
FWIW, I camethisclose to trying a Klyne 7LX-3.5B also, but the timing and finacing didn't quite work out. Alas, I guess it wasn't meant to be.
Cheers,
John