how do I rig 2 preamps to one power amp?
If you can find an a/b box which will switch remotely (or simply wire a cable in place of the existing switch) you can use the Patchwork to select the active preamp.
Additionally, you can plug your guitar into the Patchwork input, plut the Patchwork main out into the power amp and then place your preamps in two of the loops.
If you do this, however, you lose the ability to switch effects in between the amps. *To make this work most effectivly would require two Patchwork units.
I'm not positive, but I think the loops on the RFX Patchwork box are TRS-jacks and allow for stereo loops by using an insert cable (just like with the Pod Pro and Flextone HD stereo loops)