I've tried out a marshall JCM2000 TSL100 half stack and it sounds amazing! it's the best sounding amp I've ever heard. and I've also tried out a mesa triple rectofier halfstack, and it was also really good, but they fit two different styles, I'd get the mesa for hard rock/metal and the marshall for anything that needs a good overdrive (blues, classic rock, whatever) though it still has the potential for high distortion stuff too, it just doesn't quite match up to the mesa on that one.

I've never played a peavey or a carvin. but I can say marshall tube amps are awesome