For less than half the money, I chose the BAT VK-500 with Batpack option to drive my Thiel CS 6 speakers. I considered the ML and Krell amps, but don't think spending two or three times the money would have resulted in that much better sound. My pre-amp is an ARC SP9 Mk II.
Amp upgrade ?
I have a handful of amps in mind that I would like to upgrade to but I can't decide, #1,pass aleph 1s #2,Krell KSA 250 #3,Bat vk-500 #4,Sim w-5 #5,Mark lev 23.5 my current system is B&W 804 pre is audio research sp 16 cd player sony scd-1 I have heard all of these amps but in different system configurations even though some are much older than the others I think the krell and mark are still good units.