[Wayne A. Pflughaupt]

Anyway, as I have to take my mains pre-out to power the PAMP for the bass drivers in a biamp setup, could I introduce another BFD and use both channels to provide the same sort of EQ to my main bass drivers as I do to my sub?

The BFD is generally thought not to be a good equalizer for the mains – the typical complaint is that it sounds “gritty.” This is probably due to its cheap AD/DA converters. However, in the application you’re describing, using it for lower mid-range and below, it might work okay. Still, I think I’d be inclined to use a better quality equalizer. I wouldn’t be too thrilled about having another analog to digital conversion either.

I could also introduce a shelf filter which would mimic the roll off of the speaker at 450Hz @ 18db. In this way would I have a psuedo active crossover prior to amplification of the bass drivers? If so then that would also tend to improve the load on the power amp for bass duties only.

Probably not a good idea to use the shelving. Let the speaker’s crossover to their job.

Regards,
Wayne