Actually any speaker that is setup for bi-amping, i.e. they have 4 terminals, will still use the internal crossover. The high end side will still have it own hi pass filter to remove the low frequency and vice versa for the low side. Although the 976 manual is not specific on this most processors with Balanced outputs also drive their unbalanced outputs simultaneously. Therefore I would use the balanced out put to drive the amp channel that would be attached to the low end and use the unbalanced to drive the amp channel attached to to the high end of the speaker. This should get you the Bi-amping you desire.

Now, on an entirely separate note, just because you can do something doesn't mean you should. If you have a good enough amp you usually won't see any improvements when you Bi-amp. Now if your amp is under powered you might see some improvements, but that's typically not the case. I think where XenonMan was going has more do to with using active crossovers. In this case all the filters are applied prior to the amp. However, in order for this to be truly effective you would need to bypass the crossovers that are internal to your speaker. Furthermore, you will need a great deal of understanding about creating crossover circuitry, which involves knowledge of the transducers, the cabinet, the cabinet design and so on. Even in the DYI community, most people still use passive crossovers post amplification.

But hey give the Bi-amping a try. It's only a few extra cables and some time. Maybe it will be a noticeable improvement for you. Let us know what you think.