i also have a b&k(6 ch w/trim),i used to have my b&w 601s bi-amped,but when i rearranged i just went back to normal.(it was just a test to see if i liked it(i did) with a mix-match of cables).

i am waiting right now for my PE order(within hours) to set up a biamp again.ordered some 'Ys' and new speaker cables(all dayton cables are 25% off,so couldn't go wrong) we'll see how the build is when i have them in my hands.

my thoughts are that you would be better off to use a decent 'y',it would be cheaper (unless you already have balanced cables) and i KNOW it works. that's the beauty of (most) b&k amps,the trim controls.

oh,and i don't own a 990,i'm still using 'ole faithful'(my 1050)

click below on 'blade' and there's a couple shots of my b&k with the cover removed.