I would vote definitely for the Bryston 4BST. I owned a Krell a few years back (can't recall the model number, it was made in the early 90's, so I can't comment directly on the 250A). It was a good-looking amp, heavy, lots of slam, but really quite colored (that is, it just didn't sound natural), and extremely unreliable. Had to send it back three different times for major repair and was lucky it didn't blow up my speakers (power supply cap failures and I'm not sure what else...). That gets awful expensive at around 100 lbs, not to mention a pain in the...). Since then I've owned the 4BST and it was a wonderful sounding amp, vastly more neutral than the Krell, and as for reliability, the warranty speaks for itself.
Krell KAV-250a: good? vs. Bryston 4B ST at price?
How is the Krell KAV-250a? In terms of weight, size, and price it seems like "Krell Lite". How would you compare it to the other Krel amps? How is it at it's price point? Recently discontinued, they can be had new for about $2000. Is it worth it? Or for around the same money are you better off with a Bryston 4B ST (which has similar power ratings)? What else around that price and comparable output levels would be better? These would drive a pair of Mirage M-3si speakers, and be feed by a Sonic Frontiers preamp.