sub suggestions for sony amp.

I recently got my hands on a Sony XM-GTR2022 amp, and a pair of Polk momo 12's. Well after 3 days I found out one didn't work at all. So I then wired up the single working sub in a 12" sealed box i had, and after another day I blew the sub, or overheated it, or something not sure to be honest, it still hits but it's very "hollow" sounding like something in the unit separated. I'll admit i found it on CL bought them installed them and knew nothing about the gains or anything had it cranked and I'll say i payed for it. The only thing I seemed to do right in the setup was run the proper wire size via suggestions on this site. TLDR Sony amp: Max Power 1200W x 1 RMS Power output @ 2 ohms: 600W x 2 RMS Power output @ 4 ohms: 250W x 2 Variable 50-300Hz low pass filter with 12dB per octave slope Low boost 0-10dB (40Hz) What sub suggestions for this amp, or better yet what would be acceptable watt rms/peak for optimal sub selection? I've learned a bit more about not setting the amp gains up all the way like an idiot.

Ha, forgot to add car info it's an 01 Grand Prix.