I've never played the Grand Prix, but I had an Interstellar Overdrive in a rack rig for a bit. That one sounded great. Might be another one to add to the "what-would-Sushi-do-with-this" list.Has the possibility of a Sushi take on the SWR Grand Prix preamp ever come up? A friend of mine just got hold of one and I had a try of it last night and it's really great sounding.
I don't know if it's sonically similar to anything already in the lineup (I didn't have my pedalboard with me to try and compare) but it was pretty awesome.