You could. I think no matter which configuration though, you will be left with an unused channel. Unless you have, or plan, a center channel speaker in you install. (I'd like to see pics one day!).
scenario 1
You could use the 4-chnl section solely running 2 sets per channel at 2 ohms. Which you could do with a standard 4 chnl. Leaving 3 chnls free for something else. Which you could run the 9's from the higher powered channels.
= 100w x 4 at 2ohm (fnt & rear) and 50w x 2 @ 4ohm (9's) and 1 chnl left over.
Scenario 2
You could run 2sets(front) to the higher powered channels at 2 ohms then run 2sets(rear) to a set of the other channels. Or even 1 set to each of the remaining 4channels. Then you would need the 400.2 for the 9's.
= 125w x 2 @ 2ohms (frnt) and 100w x 2 at 2ohm (rear) with 3 - 50w channels left over or 50w x 4 at 4ohm (rear) and 1 chnl left over. And of coarse 100w x 2 for the 9's off of the 400.2.
Scenario 3
Probably the most taxing to the amp but still possible. You could bridge the 4chnl section to the 9's and run all 4sets (fnt & rear) to the higher power channels @ 1 ohm/chnl. This set-up would be drawing all the power this amp can produce! And of coarse all thd specs would be at their worst
= 200w x 2 @ 1ohm (fnt & rear(100w x 2 frnt & 100w x 2 rear)) and 200 x 2 @ 4ohm brgd for the 9's. With 1 chnl left over.
Scenario 4
Use the 400.2 for 2 sets fronts , bridge the 4chnl section of the 900.7 to the 9's and use the higher powered 2chnl section for the rears 2 sets.
= 125w x 2 @ 2ohms (rears), 200w x 2 @ 4ohm brgd to the 9's and 200w x 2 @ 2ohms (fnts) off the 400.2. With 1 chnl left over.
etc., etc.! whew .. now my head hurts!
#4 would be your most power and best distribution of it. I would agree with cojones though, the 2 Reactors would be mo better! But then again an 'all Ti' install would also be sweet. But Reactor = sweet too ... But the Ti's with the EQ and Power core .... I'm not helping am I
