What 2 channel Amp would you Buy for $6k?

Classe has always sounded a little lean to my ears, so if you're after "warm and rich" then I think you should scratch that from the list.

Not a lot of experience with SIM so I can't comment on that.

Of the three I'd say that the McIntosh is closest to what it sounds like you're after but I still think you should consider the JC1's.  

Dealers will let you bring them home for a weekend for an audition.

Good luck with your decision.

Classe and McIntosh are classic pairings with B&W, I don't think you can go wrong with either one. I do think you are on the right track, adding more power to your system. I've owned a lot of McIntosh but not the MC452 so I can't say exactly how that would be, I can only add that for the same dollars you are looking at spending (or even less), you can buy a pair of MC501's (that's me recommending stuff I own). The great thing about the McIntosh is that you won't lose any money on resale if you try it and don't like it. The Classe will hold it's value too if you get it at a rock bottom price. I have only heard Simaudio gear with Dynaudio speakers and can tell you it was impressive.

Classe is closing its doors...may affect it resale value
McIntosh on the other hand works very well with B&W and has a steady resale value

What would anyone pay for a brand new McIntosh Mc501 Power Amp? Is $5k too much?