Bryston 4B or B&K Reference 4420

I am using a pair of Usher Audio X-719's. I'm going to buy a new amplifier. I was thinking of the two mentioned. Which would you prefer and why?
I've owned Bryston 7Bs for 5 years so Bryston would be my pick based on probably better measurements and 20 year warranty. However, B&K is obviously doing something right to having been in business this many years.

I'd also suggest you take a look at ATI's AT2000 or AT3000 series of balanced amps as well. I use an ATI amp in my office system.

ATI AT3000
The Bryston is hard to beat. The 20-year warranty is just a(significant)added bonus.
I've owned three B&K's over the last 15 years and have been happy with their overall tone and image. Very smooth and very sweet sounding. I used them for magnapan 1.6's, B&W NT6 and soliloquy 5.3's. The first two are power hungry speakers that the B&K drove very well. However, in recently comparing my 4420 to a relative underdog, NAD216thx amp, it lacked the detail that I am wanting from introducing better cables and interconnects.
I honestly had a fantastic experience when I took two of these NAD amps and ran them bridged to mono, one for each channel. In that configuration the NAD's had comparable ratings. The soliloquy 5.3's that have a silk dome tweaters. They have an built-in smooth sound (sort like a proac speaker) in comparison to the B&W or Paradigm metalic tweeter. With these speakers, the separation of voice, piano, percussion and horns on something like Diana Krall- where favorable to my ear over the smoother image of the B&K.
I remember very fondly that the B&K had a very good affect with the B&W speakers though. Those speakers were very fast and crisp, so the B&K smoothed them out slightly, and the image was big and coherent. And, as I mentioned before, the high current of the 4420 just absolutely opened them up! They just would get louder and stronger the more I pushed them.

If you're still with me I'm sorry I've never auditioned the Bryston, but if warrantee is a issue, I recently sent my 4420 back to B&K and for $100 they went through it 100% and sent it back to me in their words, "better than new".
I had a B&K awhile back, and really liked the amp and Pre. But I had kind of given up on them as they have really gone Home Theater, and abandoned theire nicer preamps. They are still making a few 2 channel, but unfortuinetly not their main focus anymore.