A fast slew rate would be nice as well. That will lend more definition to your lower octaves. Actually, between 100hz and 400hz, there's a whole bunch of music present. Baritone thru Soprano, trumpet, piano, cello, french horn, sax, a lot of percussion and harp all have over half of their fundamental tones below 400hz. In other words: If you skimp on an amp to use there, it's gonna mess up a lot of your reproduction. You also have to consider that the slope of you crossover will have the bass amp still contributing to the music for at least another octave above the 3db down point. That means it will affect almost your entire midrange to some degree. If you don't use a well defined, fast, accurate amp: expect your music to suffer greatly. I'm bi-amping, crossed at 60db/oct(10th order) at 250hz, using a Hafler TransNova 9505. It's fully Class A and differential thoughout, JFET input stage and MOS-FET output. I don't know if I could live with it full-range, but it's wonderful as a bass amp. Then again: With a sixty day satisfaction guarantee from Same Day Music on the Behringer A500, I'd have to give it a try at least(could be a pleasant surprise). (http://www.samedaymusic.com/product--BEHA500) Contact VTL and I'm certain they will give you all the info necessary on triode operation of the 100's.