can i bi-amp my speakers with a rotel 6ch amp?

Sure you can. I now have a three channel amp, (and several monoblocks) but in general I have found several 2-channel units to be more convenient. Reasons include:

1. Multichannel amps can get darned big and heavy. Hard to locate, expensive to ship, and hard to move around.
2. If one channel fails, you loose six while repairs are made.

First let me confess, I am an adicted biamper...but...

What's all this talk about Y-adaptiors for bi-amping? What you need is an electronic (low level) crossover. If you drive both amps full range, most of the advantages of biamping are lost. Back when 25 watt amps were considered high powered, and IM distortion ran 1 percent or more, biamping made lots of sense. Today, if performance per dollar is your criteria, one better amp wins.