I found one way to do it. The results aren't that good though. I used the main cr output from the firepod to the input 2 of the Psa-1. Then I used the right output to the line input of the firepod.
I had to keep the main level almost all the way down on the firepod to avoid feedback. And the sound quality wasn't very good.
Anyone tried anything else? Maybe I'll try to use the effects send from the Psa-1 next.
E: The manual of the Firepod isn't much of a help.
E2: Ok, I just figured it out. I think I had the Mix knob set wrong the last time.
This is how you do it:
Take Main CR out from the Firepod, insert to Psa-1 Input2 set to 0dB. Then I took the effects send to line in of the Firepod. (Inputs 3-8). The trick is to have the mix knob of the Firepod set to playback (full on clockwise). This will avoid all feedback.
I already got some pretty good results reamping some bass tracks. I'll try some kick and snare tracks when I have the time.