I have a tube amp and a SS amp and have thought about doing the same thing. However I don't really understand what is needed to do so. I guess some kind of crossover attenuator is required to match the two amps. If I just put the two amps on each speaker chances are the volume will be different on the upper and lower drivers. Also, I don't really get the benefit of driving a tube amp full range into the passive crossover for the mid and tweeter. Won't the amp sound better if it didn't see the low frequencies at all? Would putting a device to handle these issues between the pre and amp create new problems (more cables, less transparency)? Anyway, that's why I haven't tried it yet.