I am a newbie trying to make my sound system sound as best as possible. As a result, I have been buying used items hodge-podge off of ebay for an upgrade. Hearing that B&W speakers are top line, I started with those. Thus far, I have B&W DM610i speakers for my mains (but they are 4 ohms), and I have B&W DM302 (8 ohms) for my surrounds. I am still looking for a cheaply priced B&W center and a decent lower priced powered sub, but I first need a decent receiver that will power the 4 ohm B&W main speakers and sound the best for music and movies on B&W speakers. Any advice? As I note, my price range is $500-$700, but I am willing to go refurb. I am presently considering the Onkyo TX-SR601, the HK 525, the Pioneer Elite 42, or the NAD T743. What do the experts think?