I don't know who told you that from Yamaha, but that's just not true. Even the lowest model Yamaha outputs the full channel of sound and is not "made" for satelite/subs. Unless it's a specific Home Theater in a Box... but the model you bought will output a full range 20-20K signal without any problems.
My friend has the 5730 and we even hooked it up to my B&Ws and it played fine... There is something else (with your speakers) that's going on here).
All it would take is one crossed wire for you to have no bass out of the speakers and for the phase to be completely off.
I'd check your wiring again just to make sure, undo the wires and plug a set (2 wires) in at one time, test, see if it sounds good, then try the other ones.
Unless there is something seriously wrong with the Yamaha Receiver, that's not the problem (at least it doesn't sound like to me).
