That's a fEarful amount of power. Can't really imagine needing that much, certainly not more. I'm on the fence between getting the 3000 DSP now or waiting for the 4500. Let us know how your 3000 works out; are you using any sort of outboard hi pass filter on your rig?
I would be very very careful when running an amp as powerful as this with bass cabs. With that amount of headroom, you'd certainly want to think about a hi-pass in your chain and you'd want to be a light touch on the power amp's attenuators. You're looking at the 700-850 range per cab if you're running either one channel at 4 ohms or one 8 ohm cab per channel. I seriously considered this amp, but was strongly cautioned to consider carefully. In the end, I decided if I wanted REALLY big power, I could bridge the IPR3000 at roughly 3kw, and I could my whole rig off of either one or both sides as needed.
This amp for me will double for PA duties as needed, when we show up to a gig and find a practice PA for the front end, or no monitors, or both. On a loud stage, it may double as keyboards on one channel and me on the other...or it might be a side fill amp for the drum riser. If its a really dodgy situation, we can use it for both small front end and monitors and I'll just use my LMII.
I'm going to see if I can get away without a high pass, but it's definitely a back burner option for me right now. The fEARful cabs are less prone to the kind of failures that many speakers suffer from the sub-30hz set, but its not immune.
Let me know how it works out. I was reading up on it, the crossover function it has, does that mean you can dial in one range for the woofer for one channel, and dial in higher range for the mid driver for the other channel?
Unfortunately, due to our singer being on 'African time' he didn't show up at my house until over an hour after practice began, and of course it takes 20 minutes from my house...so running late, my IPR sat in its cardboard box in the trunk of my car, along with my Kern preamp.

I saw this coming, so swung my shoulder bag full of LMII over my arm and used that for the evening. Man, even though I've only used the Kern once, I REALLY missed it.
The crossover on the IPR isn't really suited to fEARful purposes, more for PA usage. The 100hz crossover is too low to effectively split signal for these cabs. You'd want a dedicated crossover unit that you could program, or you could wait for the IPR-DSP amps to come out and have that function built in. As it is, that switch is designed to allow subwoofer use on one or both of the sides, or to high pass at 100hz if you're driving the non-sub parts of your PA.