I'm not sure if I understand your explanation but it sounds like you are using only 1 channel of each amp and then paralleling the drivers to that channel. You didn't mention that you were bridging the amps. If you are not bridging, you should use "Y" cables at the receiver's pre-outs to feed both the 2100 and 7100 main-ins, Then use the left speaker "A" outs for your left drivers and the right speaker "A" outs for your right speaker (1 channel for each driver for a rotal of 4 channels). If you are bridging the amps, then you are putting a very low impedance to each amp (bi-wiring not bi-amping).
Biamping progress- but is it ideal?
And the odessey continues. I'm biamping my office system, here's what I've done. I have a NAD 7100 receiver, and a NAD 2100 amp (NAD recommends the 2100 as a biamp with the 7100, same amp). As per NAD's website, I removed the shorting link from the right preamp output on the reciever, and used an interconnect to connect to the 2100 amp's left input, no problem's. Here's where I'm not sure I'm doing the right thing, speaker connections. My Totem Rokk speakers are bi-wirable, with shorting bars, which I removed. I then ran 4 ft runs of 10 gauge wire from the receiver, one run form the Speaker "A" left output, one from the Speaker "B" left output to my right speaker. I repeated the same thing with the 2100 amplifier to the left speaker. When I push the Speaker A and B buttons on the receiver, and amp, all drivers are functional. The question is, what I've done works, but is it the best way to do it? The only option I see is leaving the shorting bars on the Rokk's and using a single pair of speaker wires per side.Thanks, Jeff