I recently read a thread where people were having issues with their ARC amps, and it was mentioned that some preamps do not play well with ARC amps and could cause problems with them. I have no idea about the details of this or if it's correct, but I'd at least look into this and see if your preamp is a good match if you ultimately decide on an ARC amp. I'm sure others know a lot more about this, but just wanted to bring it up just in case it's a legitimate issue. Best of luck.
Audio Research REF 75 vs VAC Phi 200
Anyone compared these two highly rated power amps? Both companies are well regarded in the audio community. These amps sell at approximately the same price point. The VAC may have a little more power.