I understood that the main advantage of bi-wiring and bi-amping is that the speaker cables carriy a reduced set of frequencies.
Yeah, I know, the amp's sending the same signal down both wires...only it isn't.
With the individual crossovers on the separate pairs of binding posts what we have is two separate tuned circuits. The one going to the bass speaker is tuned for low frequencies, and therefore that's all that can easily travel down the wire. Likewise for the wire going to the mid/high crossover.
The upshot is that the mid-high frequencies effectively have their own cable and won't be swamped by the low frequency signal, which is far more powerful.
Some of that's what I read years ago and some of it's what I worked out so it isn't gospel, I think it's right though.
Here's a question: when I connect my front speakers to the A+B outputs on my amp does that count as bi-amping? Are the outputs driven by separate stages or are they the output from the same stage but with separate connections and mute buttons?
BTW here's a 7.1 amp for £450 that allows you to configure it as 5.1 with true bi-amping:
http://www.superfi.co.uk/index.cfm/page/moreinfo-2.cfm/Product_ID/2396