Biamp? How does this work?

Bi-amping and even tri-amping can give VERY good results, but it can be difficult to match up the amps and the volume gain will only be about 3dB or 6dBwith tri-amping. However the load your amp sees should be simpler leading to less overheating. The easiest solution is to use identical amps for all frequencies or similar ones with slightly different power (e.g. a Bryston 4B-ST dfor the Bass and 3B-ST for the treble- again getting the gain right can be tricky). With identical amps the speakers take care of everything and no special adjustment is needed. If your pre-amp has only one output you will need a splitter or a special cable (a sort of bi-wire interconnect with one set of RCA's going to 2 sets - any of the companies that custom terminate their cables should be able to make this for you). If this all seems too much you could go for a monster amp (I noticed a pair of Bryston 7B-st's for sale, for example) but bi-amping can sound great.

Good Luck

Bi-amping works - AND WELL!

By "HOW" I suspect that you mean "What is happening (re bi-amping) that is different than using a single amp with greater power...?"

The amps work more efficiently - each amp reproduces a limited bandwidth - as opposed to full bandwidth (bass or mid/high's as opposed to all). ...So, your amps do the job with less effort. Aside from offering better dynamics this can often give a sense of ease and control that is absent with a single larger amp.

BUT

Matching the GAIN of both amps is quite important. Using different amps may cause problems. i.e. If the amp you are using to drive your subs/woofers has greater gain (than the amp you are driving your mids & or tweeters with) the bass will be unnaturally emphasized. ...Imagine really strong overpowering bass.

These comments don't even take into consideration the issues regarding the integration of sound. i.e. Two amps of different makes (or different models within the same make) may sound very different. This can cause an otherwise good sounding speaker to have a “split-personality” - sound really incoherent.

Bi-amping works for me also. You can also use solid (1 male to 2 female ) audio adapters (phoenix gold or monster) out of your preamp. But, you need twice the number of interconnects and speaker cables. Depending on the amplifier and speaker, this can make a big difference or you may notice little change. Classe and others make 6 channel amps that may suit your purposes better as far as matching tonal charachteristics of amps. I would get the audio adapters and borrow cables/interconnects to see whether this works in your system. Good luck.

You cannot biamp a biwireable, or tri-amp a triwireable speaker using 2 amplifiers. Your triwire terminals connect in this way:
hi terminals connect to a high pass filter consisting of capacitors and maybe inductors, then on to your tweeter.
Your mid terminals connect to a bandpass filter consisting of capacitors and inductors, then to the midrange.
Your bass or low terminals are connected to capacitor/inductor low pass filter, then on to your woofers.

You cannot tri-amp unless you run your preamp signal out to a 3 way active/electronic filter,(active crossover), which splits the signal into bass/mid/treble outputs. The hi-pass xover output then drives a seperate power amp connected directly to the tweeter. The mid pass xover output drives another seperate power amp connected directly to your midrange. The low-pass xover output drives a 3rd seperate power amp connected directly to your woofers.

You would need to open up your cabinets, remove all the passive xover components,(ie; the inductors and capacitors), and solder the tweeter terminals directly to the set of hi-pass terminals on the cabinet back. Then do the same with your mids and woofers to their respective cabinet terminals. You will then need a 3 way active/electronic xover, and 3 stereo amps.
The xover has level controls for setting frequency, and relative loudness levels between the bass, mid, and tweeter speakers in the cabinet.
Bi-amp assumes a 2 way system. Bass and mid/tweeter. You need the same direct connection of drivers within your cabinet, a 2 way active crossover, and 2 stereo amps.