I purchased a IPR2-7500 tonight for my pair of SI 24 subs. Will try to have two tall, slender 15 cubic ft boxes made for them in January. I'm also flat out bored of my Yorkville U15s so I should have four of them sold on this saturday. I then plan to get a second pair of Yorkville U215s for my rears when I can find a used pair on CL or ebay with shipping. So I won't be going back to a 7.4 system. Too many potential problems, more wires, more amps, and more all out headaches. Gonna go simple with a 5.2 system on steroids.