New or used amp?

Couldn't have said it better myself Karls, I think the biggest factor out of the two would be what you are trying to power, but I would rec. the BAT over the Bryston, just my personal preference.

I second Karls thoughts. I have a Bryston 4B-ST, and at their used price, you can't do better. They also carry a 20-year, unconditional, transferrable warranty, and Bryston provides outstanding repair service.

I had both the Bryston 4b-st and BAT VK-200. The BAT was better in all areas and had way better low level resolution. The Bryston ran cooler and had the better warranty, but had really unfriendly speaker connectors.

However, I sold both of them in favor of a Marsh A400. The Marsh is way more neutral and revealing than either the Bryston or the BAT and equally as powerful. The Bryston, in comparison, sounded veiled, dark and sluggish with undetailed (monotone like) bass emphasis; it made the bass notes sound all alike regardless of what music I was listening to. The BAT was a little thin and lean in the midrange, but much better than the Bryston, but not as good overall as the Marsh.

What about Pass X150 about $1900-2000 used. Isn't it better choise? This is a question not recommendation.

First make sure the amp will match up well with your preamp and is suitable to drive your speakers. Try to find a dealer who will let you audition the amp at your place or that will let you return it should things not sound like you want. I have bought used equipment and had good luck with it - you might want to give it a shot. Also, if tubes will work give'em a try. Cary, Rogue, VTL all have stuff in your price range.