I was using Primaluna EVO 400 preamp with Pass XA30.5, to drive Focal 1028be and to "tame" that spicy beryllium top. Was quite happy with the combination. Before Pass I had Hypex NC500 based power amp, which was also good, dynamic, but maybe a bit too dry.
Biggest problems i found were: preamp with low enough output impendence, gain will be too high (I have to use Rothwell XLR attenuators), matching speakers to pre/power combination. What worked well with Focals, maybe its not the best with some other brand (evaluating Q Acoustics Concept 500 and Scansonic mb2.5b now).
So, in short, can result with really good sound but requires much more effort (read: money to buy/sell different amps/preamps:)