Sub wiring, Amp wattage vs wire size?

I am totally a newb in the car stereo department, and am going to be putting a sub in my wifes WRX. I am wondering if i am running a 250w amp, how big of wire should I run to the rear of the car to the amp? Here is the sub I have:

http://www.crutchfield.com/p_107DXI108/Polk-Audio-DXi-108.html

and here is the amp I'm using:

http://www.crutchfield.com/S-PhEPSkpS8Yx/p_130GMX372/Pioneer-GM-X372.html

According to bestbuy these should work well together, but what gauge wire should I run, is 4ga sufficient?

 

Yes 4ga is more then enough.

 

8 gauge would get the job done as well.