Maybe I'm missing something. If he wants to bi amp why not use a Y cable on the pre out to split the signal to the second amp. Assuming he is drivng the top or bottom of a full range speaker this is a no brainer. If however he wants to drive a second sub then just put the Y on the sub out. In any event get a good Y cable or jumber. I biamp my home theater coming out of a lexicon with no degradation. Hope this helps.
Walkelin
Walkelin