B&K makes great gear. If you can, audition the Lexicon and Sunfire as well. Don't be afraid to compare the Arcam AVR300 to those. It costs less and may perform nearly as well. I would not be surprised if it was equal in many of the most important ways.
I've heard the same thing about the ARCAM and it's quality sound. If you like your receivers 'Plain-Jane' and stripped of virtually all features, you'll really, really like the ARCAM because it comes with nothing.
If you have speakers capable of good sound, not just loud sound, you need a receiver capable of delivering it. If you you have poor quality speakers it doesn't matter. Get a receiver with all the bells and whistles so that you can spend endless hours trying to achieve a sound that is satisfying. Me I'll take the good sounding gear. You can buy a Sony with endless useless features, but how does it sound?
I have good speakers. I biwire my Mirage bipolars and I have Polk Audio LsiC center speakers and FXi5 surrounds (Polk Audio). I have a SVS PB12-Plus sub which is very good quality. They only make subs. Will the B&K AVR505 be a good chice to drive the speakers?
The B&K AVR505 would be a good choice to drive any speakers. If you are buying new I would still give the Arcam a listen. It could save you alot of money. I love my NAD T763, but admittedly I would probably have bought Arcam or B&K if my plastic would have stretched that far.