Not all solid state amps sound the same contrary to popular belief! Yet not all tube amps sound the same either, even though they use the same kind of tubes. I own three tube amps, and two are EL34 versions. They sound nothing alike. So much for that.
What I've found out with the mono extremes is that they seem to have some merits that we tend to look for in tube amps, but on the otherside of the coin they don't do what tubes do in other areas. I feel that the monos seem to favor the warm smoothness I like from tubes, but are faster and seem to hit harder than tubes. As a rule they are not as forgiving as a tube amp, and errors will often jump out at you. This is not a bad thing at all, but just different. I still think I'd like a pair of C.J. ST140s as well as anything outthere, but trust me the extremes are not that far behind for less than half the price. The Plinius amps were something I've always wanted to hear as well as the Arcams. I've listened to the Krell mono blocs a bit, and the Mono Extremes flatly blow them out! The best way to put this is like comparing an Accuphase amps with the Krells. One is a tad edgey in the upper mids as well as the high end of the scale, while the the other has a tube like liquidity and is much smoother thru out the entire scale. So I'd like to think that the Extremes have something of an Accuphase sound (I do like that by the way). The bass seems to come faster and much harder with the Extremes than the Accuphase, and maybe a little more open. I might also add that I think the build quality is better with the Extremes than the Accuphase, but can't prove it. But the one thing I like better than anything else is the "made in the USA" tag I get to show off to my buddies!
Still no matter what you buy in amps, they are only going to be as good as the preamp that controlls them. So you shold really be thinking in packages here. I went with a tube preamp (that's all I have but for one combo thingy). My amps have been driven now with one S.S. preamp and two tubed preamps. The sound was vastly different in all three. Go with a tubed preamp, and never ever look back!!
gary