need a power amp to run a set of infinity kappa 9s

I have the Kappa 9s. You don't need huge power. What you need is the ability to handle low impedance. I can play mine 'LOUD' with my Son of Ampzilla 80wpch amp that delivers 250 watts into 2ohm. Even my Grandson of Ampzilla at 40wpch has no problem driving them, being similarly capable. But if you want concert hall levels, I use my LSR&D Superamp monos at 300wpch with 900 watt peak ability. The amp really has to be stable to 2ohm or lower to sustain relatively high spl without being over driven.

The dips are sharp and right at about 30hz and 7000hz. Contrary to popular belief, the published sensitivity is actually pretty accurate. It's probably the impedance dips responsible for the notion they are 89-90db. A properly matched amp will drive them to very loud levels very quickly. It is well worth accommodating them.

George, I recently sold three Acoustat TNT200 and a 120, all fully rebuilt by Roy Esposito in Florida. These amps are pure Fet, designed to drive the Acoustat line. Even in mono mode, they had no trouble driving the Kappas. The reason I sold them is because I came to my senses and realized my LSR&D 101s and 102s are superior in sq. I got them for an active JBL system. Anyway, it seems that the very nature of mosfets would make them especially suitable for low impedance loads, no?

But as I said, the Acoustat TNT200 and 120 were designed to drive low impedance loads. In stereo, the 200 doesn't even break a sweat. In mono, they get a little warm. That's driving the Kappas. They have the Hitachi T03 2SK135/J50 and the 120 has the 2SK134/J49. Roy, who was a principal engineer at Acoustat and instrumental in designing these amps assured me that they can easily handle the Kappa 9s. He was correct.

My assertion regards the inherent nature of mosfets to thermally self-protect by reducing conduction as they heat up. Seems ideal in low impedance circumstances.