fosgate r500x1d amp and 8 inch sub

My friend asked to install a sub in his 2013 GMC Sierra Crew Cab using his stock stereo. He has already purchased a box that fits an 8 inch sub and also purchased a Fosgate R500X1D mono amp. Since he wants an 8 inch sub, do you have any suggestions to what sub we should use. He was looking at a shallow mount RF P1, but will his amp be too much for a P1? I was thinking more on the lines of a Kicker Comp VR or just a Comp. Here is a link to the amp that he has purchased: http://www.crutchfield.com/p_575R500X1D/Rockford-Fosgate-R500X1D.html?tp=35834 He wants a setup like mine in my Ford F150 but cheaper. I am running a single 8 inch probox sub, in a ported probox under the rear seat. Its running off of a JL Audio JX500/1D mono amp. I think the probox 8 inch sub can handle up to 450 RMS. I did not install the system in my truck, purchased it with it already installed.

Here is some info on the box: Measurements Width: 26" Front Height: 9" Back Height: 5" Depth: 15 3/4" Airspace: .80 Cu.Ft. Per Chamber Subwoofer Mounting Depth: 5 1/2" GMC Sierra Crew Cab Single 8 inch enclosure Here is the sub he was looking at purchasing: Rockford Fosgate P3SD4 8

http://www.woofersetc.com/p-10522-sa-8-v2-d4-sundown-audio-8-dual-4-ohm-sa-v2-series-subwoofer.aspx

The shallow subwoofers are for trucks with no room for a full size box. If you want a nice 8 inch sub look at the Sundown audio subs. If your just using one then get a 2 ohm 8 inch sub. you will up the power on the Rockford amp. Sundown audio make nice subs for the price.