Has anybody used Krell HTS7.1 entirely as 2 CH pre

I'd go with a Krell KAV-280p Preamplifier for your set-up over the HTS. The KAV Pre has much technology from the excellent KCT Pre, since it was designed a couple of yrs. later. Maybe 85%+ of the KCT's sound when run-in balanced mode. You could pick-up a new one at the low-end of your price range.

Sstalwar: I currently use the HTS7.1 as a two channel (sometimes 4 channel if you include the center and sub)pre/pro. It works flawlessly for me and redirects channel input as required. Programming it is easy, even for me. I drive Maggie 20.1s with fpb350Ms and the center/sub with a Krell KSA 150S. FWIW, if I had to do it all over again I wouldn't hesitate to get the HTS7.1. Later if I decide to go surround, it's ready to go.

Sorry I can't give you a comparison with other pre/pros - only validation that the HTS7.1 does a heck of a job.