I own a B&K AV receiver and a separate 2-channel amp. I completely agree with highfigh and walter. With emphasis that B&K
was a good company, but they are now history.
I guess one thing that might be different is that I bought all my B&K gear used. And unlike walter, who has owned a wide variety of electronic gear, all the B&K stuff I have, compared to my previous Denon, are the best I've known.
A feature I really like in the both the B&K receivers and the pre-pro is its built-in digital parametric equalizer. It allows you to create a narrow notch filter to eliminate room reflection caused bass peaks. I think this works very well, and, in my opinion is much more likely to work well than any of the automated systems available. For a better explanation,
download an AVR 507 S2 or Reference 50 S2 manual, and read pp 27-28 (in the AVR manual).
The THX rated 500 series AVR and pre-pro allow making one notch filter. The series 2 models, like walter's, allow making 3 notch filters. They dropped the THX rating for that model and made better use of the space it freed up on the digital chip(s). If this makes sense and appeals to you, I would look for a used AVR505 or 507 series 2 receiver, or a Ref 50 series 2 pre-pro. For a better explanation, download one of the manuals still available online,
So, with that in mind, what are you looking for in a receiver? If you only want the ability to add external amps, a used B&K AVR or pre-pro might be a good way to go. You would buy at a price that takes into account that there will be no factory repairs available.
If you are also interested in HDMI connection and all that related software, you probably are better off staying with the big makers. I would avoid the newer B&K 700 series. It will cost more and may require more software upgrades that will probably never come.