What subwoofers for the rockford fosgate t1500-1bdcp

Hi all, very new to the aftermarket audio scene but looking for some information on subwoofers. i will be getting the Rockford fosgate t1500-1bdcp. birth sheet says 1980 rms at 1ohm. the guy selling it is recommending two Rockford t1d412 subwoofers or two phoenix gold 12 inchers. cant find much info on the phoenix gold, but the rockfords are 800 rms each. I'm also open to suggestions on other size subwoofers and more than 2 subwoofers. my main question is what subwoofers should i get for this amp. do 15's hit harder? and are there any prefab boxes that sound good with the rockfords or should i just get a custom box. thank you. budget 2k and car is a 2004 fx35