It's probably a bit more work than you'll find worth, but you'll have to get a power supply that is capable of AC/DC conversion from the wall to the amp and has sufficient output to correctly drive the amp and drivers. FYI, good power supplies aren't cheap...
What I'm getting at is you may just want to pony up for a good dedicated amp that was purpose built for driving home theater subwoofers. You didn't mention what 12's you have, and that will determine what amp you should look for.
For something with similar specs you would be looking at something like the Emotiva XPA-100 amp. But just a word of caution, depending on the enclosure of the subs it may not sound quite as nice in a home stereo/theater environment as it does in your car (which usually just targets high SPL and not even frequency response).
Alternatively, you could use a computer power supply to provide power to your car amplifier. You would need one that could provide at least 30 amps and you would need to do some customization to it in order to run your amp.
Yeah, unfortunately a monoblock 300w amp isn't going to be cheap. A lot of home theater subs come with a plate amplifier built-in. You could alternatively buy a plate amplifier, something like this. This style of amplifier is typically part of the speaker enclosure, so you could cut a hole in the dual sub enclosure, or create a custom "enclosure" for the plate amp by mounting it to a board separately.
You should just sell your car amp and subs and use the money towards a proper home sub. Car subs are made in mind that the cabin gain will boost the low end. When you put car subs in a house there's not nearly enough cabin/room gain to help out the subs and they end up sounded very weak, you'll wonder where the bass went. You could put them in a new box but more than likely it'll be huge. More trouble than it's worth IMO.
There are reasons why home theater subs are different from car subs, and I agree that buying a new subwoofer is going to give you the best sound. If you decided to use the plate amp, you could build a small box to mount it to, and run the output wires to your subs from there.
If I were in your position though, I would try to sell the car audio equipment and buy dedicated home theater equipment.
You could also use this ($40) to power the amp. It would require some soldering or stripping and crimping in order to connect it, but it has more than enough power for the amp also.
You would just combine one of the yellow wires from each rail, and connect that to your positive terminal on the amp, and the same for the black wires adjacent to the yellows and connect it to the negative. Then to turn the power supply on you'll need to short pins 14 and 15. Then you would use the power switch on the back to turn on/off the power supply
So I'm leaning towards to just selling both and possibly buying some home subwoofers and such. Any suggestions?
I really think my car subwoofer is plenty heavy on the bass seeing as I live in a small, college apartment, but I guess i'll just trust you guys. I don't have a soldering gun here at college, but I believe those are cheap, so I might even go that route. We'll see.
Check out the Dayton Sub-1000 and Dayton Sub-1200 and the BIC America F12. They're all on amazon, and probably the best budget subs that exist. If you are looking even cheaper, second hand subs can be an option. Check eBay, craigslist, or audiogon, or if you're in canadia there's a secondhand audio site canuckaudiomart.
I'd post links but I'm on mobile.
Look up reaction audio subs. New budget company making great subs on a budget. I think they have a b stock bps 212 which I have heard personally, and for it's size it's very impressive. I heard it next to it's big brother the bps 215 and it was definitely holding it's own, just didn't have the extension the 15 had, but was plenty loud.