as long as the 4 ga is not split to anything else and make sure it's a good 4 ga, at 15 ft with an amp drawing that much current you'll fry cheap 4 gauge.
With some good 4gauge you'll be fine. If you go bigger, just get a distro block, (or fuse block) mount it next the to amp, run the 1/0 (or whatever you use) into that, and then a short piece of 4gauge to the amp
much easier to run 1/0 the first time than to pull out the 4 gauge because it wasnt enough. I dont think that the AQ needs bigger than 4GA. by itself but its nice ot be able to upgrade.
just run 1/0, in the long run, it will be cheaper. put a distro like this one http://www.woofersetc.com/index.cfm?fuseaction=product.display&Product_ID=6316 it sells for5 bucks on ebay, and a small, very small, run of 4g to the amp, and you will be fine, and then in the future if you even want to upgrade to another amp or anything, you have the power in the trunk already with a open output onthe distro.