Amp Help WIth New Sub

I Just bought a new Rockford T115D4 15" dual 4 ohm subwoofer with box and have no idea if im running an amp that will do the trick. Its a Polk-momo 500.1 carbon series mono amp that i was running my 12" type R with (which im selling). I hooked it up this morning, and its hittin nice and smooth but im not sure if im doing anything to harm the sub (ohms, watts, ect). Pleaseeee help, thanks