Installed my oem sub last month. Push the watts, you'll hear the oem sub limitations, but low to mid volumes sound good, well, better than not having a sub.
Eloquently stateddo not buy any oem audio equipment from Subaru. it will be beyond shitty. you can pay me, ill punch you in the face and that will be a better value. you can buy real stereo equipment for not a lot of money.