Can I use a multichannel amp to bi-amp my speakers

To biamp effectively, you really need an active x-over. I don’t know how you could use that while also using a single multi-channel amp to drive the speakers.

I think the amps you are considering would work better than a multichannel amp. I also noticed more improvement in sound with a better single speaker cable than bi-wiring with a lessor cable.

... I know that Gershman uses Nordost Red Dawn as interconnects and speaker cables and I'll probably go that route as well... I am leaning more towards the ModWright and will go Bi-WIred...

I use single Kimber 4TC unterminated wire so part is spliced for lower terminals and part is for upper respectively on the speaker end.
It looks like biwiring, only I don't have to use jumpers.

A multichannel amp will only work to bi-amp if each 'amp section' has it's own input, which (as noted) requires an active xover.  In my case, I've dispensed with a pre-amp, gone to active eq, and use a matrix (actually a pair) to control inputs and how various elements interconnect.

I really don't miss a stand-alone pre-amp, BTW...