Tri-amping speakers - Which amps

I am seriously looking at running a tri-amped system with an active crossover and 6 channels of amplification (the speakers will not use passive crossovers). The speaker designer suggested 100-200 watts for the woofers.
With that in mind an obvious choice would be a 6 channel amp from someone like ATI or others. Another alternative would be to find 3 used stereo amps. Something like the B&K ST140 would seem like a readily available possibility, but that model is fairly old and repairs may be expensive. I guess I am 'testing the waters' with this setup and do not want to spend a fortune on amplification. I can always sell the active crossover and have the passive crossovers hooked up in the speakers, but a 6 channel amp would be hard to find other than new and I don't think the demand would be great to try and sell used. Any sugggestions/