I have bi-amped the RM40s with Ampzilla 2Ks, Classe (somewhat warm sound), and Marsh (clean and articulate) at various times. Unlike the RM/X which practicallly requires bi-amping, adding the second set of Ampzillas to the RM40s only created a marginal improvement. The use of the Classe or Marsh for the mids/tweeters were both downgrades to using the Ampzillas full range.
Generally speaking, your choice is either get a high quality tube amp or try the new Son of Ampzilla. Off the top of my head, I can't think of any other SS amps under $5k that I would reasonably think would be an improvement over your full-range Ampzilla 2Ks.
Also, if you are not currently bi-wiring with your Ampzillas, I HIGHLY suggest you do that first. Use a true bi-wire cable and not just a jumper to get the best results.
Julian
www.sedonaskysound.com
