My personal experience with B&K amps are excellent. I currently own a 3 channel B&K.
A friend of mine has B&K monos and they are excellent. BUT, I feel my Stratos Stereo amp (cap upgrade) still sounds better (although our system synergies may be different). They are very conservatively rated at 180w and have a 20 year transferable warranty! You can also buy, listen for 30 days and return it if you are unsatisfied! You can even call Klaus on his phone and guess what?...he'll pick it up and actually talk to you! He even gives unbiased advice! Ack! Can this be true? Why yes it can!
If possible, listen to your candidates. If not, buy something you can return for a full refund. If buying used, you can always turn around and sell it for what you paid for it (assuming you don't get ripped off).