Big watts are unreliable due to heat. A friend used to own the larger FPBs and the amps showed leakage with the capacitors or some other components. The cost of maintenance may be high. Personally, I would not go higher than 200W for Class AB solid state amps. For higher power requirements perhaps look at some of the Class D options. Alternatively explore more efficient speakers.
Big Krells Have Vanished From The Used Market
Once upon a time several years ago, you could always find several of the big Krells for sale on Audiogon. I'm talking the 500-750 wpc big irons. Now since Krell no longer makes anything bigger than 500 wpc, anyone with the 600, 700, 900 wpc amps are holding on to them because there's nothing new by Krell to replace them with.