As the skipper posted, a tape out connection is not the ideal place to connect any subwoofer. The level is fixed and doesn't track the volume control.
All things considered, a 12" sub will generally play louder and deeper than a 10" sub.
For setup:
Do the subwoofer crawl to find the best place for it. Set the phase selector switch at the position that produces the most bass. For the crossover setting a good place to start is the -3dB point of your main speakers. For setting subwoofer level just remember, if you can tell you have a subwoofer it's almost always too loud. set the level so that you can't tell when it's on but can when it's off. Bear in mind a certain amount of tweaking (position, level, crossover frequency, phase) is necessary to get a sub properly integrated.
