I'm thinking of bi-amping my B&W 305. My main amp is an onkyo 838 (90w/ch L,C,R, 50w/ch SL,SR). Can I purchase a stereo amp, hook it to my front L&R pre-out and use this to power the B&W woofers while leaving the onkyo to power the tweeters? What stereo amp (power, specification, etc) would be appropriate for this? In bi-amping, are there different preferred wires running to the woofer and those running to the tweeters?