I tried doing this a few times. I split my preamp output signal with part of it going to a dedicated power amp, then out to bass cab. The other portion going directly to a guitar amp, set up with an appropriate EQ to support the sound I'm shooting for. Add a bit of HPF to the Guitar Amp feed so the speaker doesn't bottom out. The guitar amp feed can be post preamp, or pre-preamp .. whatever flicks yer thrillswitch. This seems to work really well. I haven't done it at a gig ... yet! But I'm certain I will at some point soon (as soon as my drummer heals up his injured hand). I've used a Line 6 Spider 75 (2x12 open back). The Spider offers so many variables with the different amp models et-al, that I was able to dial in any number of great tones. It seemed to ~meld~ with the bass amp/cab sound just fine, and didn't sound like two different sounds mushed together. Next test will be using the Spider as just a preamp, and using a 100 watt power amp to drive one of my custom guitar cabs -- a 2x12 open back with Celestion V-30s. I'll see how that works out. This type of approach seems more tunable and flexible than using 3-way bass cabs with fixed crossovers. Or even some of the 2-way cabs that use a woofer and a 6" driver with a fixed crossover. You have so much more control over everything with the guitar amp setup. Like the total volume of the midrange, the tonal coloring and actual ~sound~ itself of the midrange freqs. As well as where the midrange is actually ~tuned~. Unless you have a bass cab with a totally tweakable crossover, you're stuck with where the midrange driver is tuned, and how loud it is, as well as what the midrange driver actually ~sounds like~. You get what the cab builder has decided is *good*, and you're gonna like it, dammit! Heheh ... Anyone with like experiences, or comments about this type of approach? Thank you! And Happy Full Moon!