Biamping and biwiring are two completely different things, and subject to much debate when you consider biwiring.
Biamping, yes there can be substancial benefit to biamping if done properly. You have to ensure that the levels are matched between the 2 amplifiers. In other words, if you use a much larger amp to run your mid woofers and a smaller amp to run your tweeters, there can be a level difference during playback where your tweeters are too quiet (of course, they aren't getting as much power). It's suggested to use identical amps when biamping, or at least close enough to compliment each other. A notable exception to this 'rule' is using a tube amp to run the high & mid frequency drivers and a solid state amp to run the low frequency drivers; that can be a pretty nice set up as you combine the low frequency power of solid state transistor amps (tube amps don't handle low frequencies quite as well as SS) with the silkiness of a tube amp for the high & mid frequencies.
Next with biamping is the type of crossover used: active vs. passive.
An active crossover splits the signal before it gets to the amplifier. In other words, it splits the signal into a high frequency signal and a low frequency signal, each of which can then be directed to their appropriate amplifier. This provides a more efficient means of amplification for each signal path as the amp driving the low frequency drivers only amplifies the low frequencies in the signal as that's all their input signal contains...
With a passive crossover (such as a crossover built into your speakers for example, with multiple binding posts on the back of your speaker labeled high & low), a full range signal (both highs and lows) is sent to both amplifiers. Each amplifier then has to amplify that whole frequency band and send it to the to the corresponding binding posts, where the internal crossover passively eliminates the unwanted frequencies and allows pass only the highs for the tweeters, and lows for the woofers. In this set up, you'll still be able to deliver more power to your speakers than if you used just one of the amps, but each amp is still working to amplifier the entire signal, so again it's not as efficient as the active crossover method described above.
Biwiring: this may just start a debate! Honestly, I have not heard a difference in biwiring. As long as the resistance is low enough in your speakers cables when you single wire your speakers, I wouldn't worry about biwiring unless you just want to experiment with it. That being said, if you do want to try it, nothing anybody can say on this forum should stop you. Just don't go buy overpriced speaker cable to try it! Again, I haven't ever noticed a difference, and I don't currently biwire my speakers; maybe I would if I still had a surplus of speaker cable, but I'm not rushing out to buy more to do so. Long story short, anybody would be hard pressed to prove if biwiring makes a difference vs. using a single run of low resistance cable.
Brad
