Here is what I would do. I would add up your RMS W (1700W) and add 1000W for your vehicle. That is about 2700W of power you need to cover. The G51 batts are good for about 1400W. So if you had 2 of the G31s you would be all set. You can put one under the hood and one behind the seat near the amps. I am pretty sure the G51 will fit under your hood on it's side. At least from what I can see online.
I would go with the S series up front and the D series in back.