So my brother has an 02 GT with a avh-4200 headunit powering his otherwise stock mach 460. He bought 2 pioneer ts-w253r subs to add but doesn't know what amp to get. I'm thinking just one of the subs will be enough punch for the mach 460. but what amp for one of them and two of them?

http://www.crutchfield.com/p_130TSW2...ures_and_specs