That would be just right for 2 BL's
As for your electrical, do the Big 3, and at least one extra deep cycle battery (yellow top, kinetik, powermaster)
Also, it would be a good idea to get a bigger alt but if you have enough batteries and don't play your music for hours straight, you should be fine with a stock alt, as long as it has decent amperage.
EDIT: Why are you going with the BL? Do you want SQ or SPL?