We all generally agree that Bi-amping is a waste... especially off your AVR, as the more Amp Channels you run, the lower the available power per channel becomes.
It is said there can be a very minimal gain in doing passive bi-amping, but only one person I know of has indicated he could hear a difference. I don't think there has ever been a published spec that shows a tested improvement in speaker performance.
In fact, several speaker designers that I've talked to, offer dual sets of Binding Posts mainly for the perceived value of it, but they don't think it adds any performance enhancement. Two said bi-wire and bi-amp is ridiculous and a waste... one said DO NOT bi-amp, but you can bi-wire if you want even though hit doesn't do anything... The third cat said he likes bi-wiring (only guy I ever heard say this!) but does not like or encourage bi-amping. This guy also sells Mil-Spec wiring upgrades to his speakers and says it sounds much better than conventional speaker wire. (I take that with a hefty dose of salt.)
Anyway, I like 12AWG pure copper wire: use it for all my runs. Monoprice fits the bill and is very affordable. Choice for regular runs. Access for in-wall runs. Same wire... just the insulation changes.
Also, if you like Bananas, their Affinity Series Banana Plugs are pretty great, available in straight and 90deg. Some reviewer bench tested them against others and found these to be the most conductive, and they have a great price.
Cheers!