OK, I figured it out!!!!! 
I first switched my preamp input to ANALOG in 3. In the routing utility I enabled the on-line mode, then selected #21 Firewire 8 Track AB. I then connected ANALOG in 3 to MAIN in 3. All the remaining Firewire ins were still connected to their corresponding MAIN in channels. This resulted in MAIN out 1 & 2 receiving Firewire 1 & 2, which outputs to my L & R speaker respectively.
I then connected MAIN in 3 to DSP B 1 & 2, and those into MAIN out 1 & 2 (on the right… there are 2 vertical columns of MAIN out 1-8.) MAIN out 1 & 2 are also routed to my L & R speaker respectively.
In sum, my firewire connection is routed through DSP A only, while my analog connection is routed through DSP B only. Both make their way into MAIN OUT 1 & 2, so I have both firewire (software instruments) and analog (audio) signals coming out of both speakers!
How does that sound??? 
