While it would be sweet to have these outputs available (how much work is it anyway? off the shelf products more or less?), I currently use my system in this kind of manner. I have the fronts for my full range front and rear splits with a Y cable at the amp, and the rear channel for the sub amp.
I have fixed the EQ so that the front has a HPF at around 80Hz, and the sub has a LPF at around 200Hz. The gain on the uppers is used to balance the F/B position. I used the EQ in Cool Edit Pro to adjust the 'look' of the settings and then tweeked it in the car.

My only 'wish' is that the eq or encoding can have 'coarse' adjustments of bass and treble. this would be cool to adjust from the Mk2 dial. the DSP is used for overall sound output and then this extra sweetening from 'tone' controls.

(push the dial button and you get the standard sound controls-> Volume (default), Bass, Treble, Loudness, Balance, Fader.)
(hold the dial button in and you can access the menus)



-- Murray
Empeg changed my life and it did happen overnight.