I have a full 5.1 based on the Zu Definition ver 1 with custom Zu center and surrounds. Please see this link for photos
http://www.audiocircle.com/index.php?action=gallery;sa=album;id=1327
Originally I had the Def's with an Energy RC300 center and Energy XL 15 surrounds. This sounded more than adequate, however once I made the upgrade to the Zu center and surrounds, it was a more synergistic and fuller sound, as they are quite a bit larger than the Energys hat I was using.
If you are looking for a receiver, I would suggest a look at the newer lineup from Onkyo/Integra, full features and nice sounding (per the HT mags). I have the Integra DHC9.9 as my Processor, and the Integra Research RDA-7 as my amp, so I would expect the newer products to have a similar sonic signature.
Hope this helps.