I have 2 of them and give them about 500 watts each daily with no problem, I think on this site or diy mobile audio there is someone giving them 700 watts apeice with no problems. I'm not sure on the gtr as I just run mine sealed with no radiator.
I'm running two G5 12" subwoofers off a JL Audio 1000 and they get loud and they sound real good. I'm running mine right at 1.0 or 1.2 cubic feet per sub can't remember the exact size at the moment.