Well as good as IDMax's are, id chose a Velodyne over one for SQ any day. Or... is your the home version only?
A single IDMax should be sufficient to keep up with a true SQ system, even when running IB. Sounds to me more like you want SQL than you do true SQ.
Either way, if you chose to keep the W7, or the Velo... sell the other and buy that second IDMax. I dont understand how you have $1000 to spend on SPL subs and amp, AND have a spare W7 or Velodyne sitting around, but cant afford to buy your second IDMax setup?