I don't think there is much agreement on whether receivers have different sounds. Some people say "yes", other people say "well you must have had something else set differently" and the issues never really get resolved.
$500 should get you a decent receiver from any of the top brands -- Denon, HK, Yamaha, Marantz and probably a couple of others. There are some real bargains to be had with re-furbed Denon/HK's and with cleared out HK models (230, 330 etc..) being replaced with a very similar 235, 335... family.
If you believe in this "receiver brands have characteristic sound" thing get an HK or Marantz because they are supposed to be a bit warmer, but I wouldn't waste your time worrying about that. Get a good brand & model at a good price, avoid the real fly-by-night places, and enjoy. If you see what seems like a good deal you can check back here for 2nd opinions on pricing etc...
I would look hard at getting a good deal because $500 can get you something pretty darned nice right now (good features and good power) if you shop carefully. If you want to play loud with small speakers you'll need a bit of power, even with a sub.
Remember that HK power ratings are pretty conservative; anecdotal evidence is that an HK at a good price has the same effective power as a Denon (for example) in the same price range.
The Pioneer 1014 is probably the wild card. Some see it as a great receiver at a bargain price, others don't like it. I haven't heard it so can't comment.
Let the flaming begin. Coffee isn't working this morning so apologies to all if I missed your pet receiver
