I've read the various posts on what balanced vs. unbalanced means. My question is, how much of a sonic difference does it actually make? Does it have any dependence on speakers, etc? Will I notice a huge difference between the 7200 and 7700?

For reference, I have:
Mains: Polk RTi12
Center: Polk CSi5
Surrounds: Polk FXi3
Sub: Non for the moment