Pre- / Amp for Eggleston ROSA

Yes they like powerful amps.

I have a friend who runs a Krell KSA-250 into a pair of Andra 2's with a Levinson front end and they sound very musical, none of the usual attributes associated with Krell sound. In fact, when a Krell amp is partnered with the "right speaker", great music happens. I'm sure there are a few other amps that would work as well also.

so how about those Crown and Hafer kind of rack mount industrial stuff? I think they may still be cheaper than the vintage Krell or Threshold type of pure class A stuff ..

They're a fairly stable 8ohm load, so they actually don't need gobs of power. I've run my Rosas with tubes and SS; currently, they're making beautiful music with Cary 805 monos (not exactly a Krell).

The Rosas are very tansparent, so your issues may involve something beyond your amp/pre (ie, source, cabling, etc.)