I use the P2000b with a McCormack amp, but I did have the A400s in my system for a while and found the sound to be relatively rich, liquid, and full sounding for a solid state combo. I didn't find the sound to be cool sounding at all, but I haven't heard the Classe gear and it's all relative. In fact, I stuck with my McCormack amp because the A400s was just a tad too polite for my tastes, but I could see how many might prefer its more laid back demeanor. Cables will obviously make a big difference here too.
I find the P2000b to be a very refined sounding piece that, while probably not quite a tube substitute, certainly creates a fluid, dimensional, and natural yet detailed sound that I would think would appeal to someone looking for some of the positive characteristics often associated with tubes. By the way, the Marsh pair really needs to be run balanced as they sound significantly better in that mode -- I ran them both ways with the same cables and it was no contest.
Sorry I can't shed more light on a comparison with Classe or how close the Marsh pair gets you to tubeland, but I will say that the Marsh gear sounds a lot less like what most would consider a "solid state" type of sound and as such may be worth consideration given your goals.
Best of luck.
