Subwoofer- 10" or 12" for music only system?

I would like to augment the bass of my music system and am wondering which to choose? Possible brand recommendations in the lower cost range would be helpful as well.

Thanks, Lee
Is this specifically for music, home theater, or both? The size or diameter of the subwoofer is only one part of the criteria to select the correct model. Size of your room, brand of your present audio system, amount of watts best for your room, how low do you want it to get in hertz, etc. It is generally recommended but not required to use the same brand subwoofer to that of your system. The materials used match and the sonic peformance and timber match. Also depends too on how low your main L&R speakers get to. If they're floor standers that can get fairly low, you may not need a real powerhouse sub. Can you get decent bass now depending on the CD being played?

Does your amp or receiver have a dedicated output for a subwoofer and does it give you a choice to select a cutoff frequency in its setup menu? Typical cutoff frequency selected is 80hz.

What is your room size and what is your system made up of?

My room is 23' x 13' x 8' and I use a 10" dia powered sub, 150 watts, freq response 26hz to 33hz, closed box, etc. I', I'm using floor standers that can get down to 38hz. Carpeting on your floor is also key and can contribute greatly to the bass extension produced. The thicker the better. Drapes and upholstered furniture contribute too. Velodyne is a manufacturer dedicated to manufacturing powered subwoofers. You may want to look at that brand. My brand is Bowers and Wilkins. Hope this helps.
Buy the larger one assuming equal quality. It won't work as hard, thus will distort less. I'd look at Hsu Research, SVS, Velodyne, Bag End, JL Audio, Paradigm, NHT, Revel... There's quite a few good manufacturer's out there. Obviously, your budget will be a factor.
I'm using a 10" Earthquake MK-IV to good effect in my system (music and home theater). As I recall, I paid $275 new in box/delivered from a fellow Audiogoner. Yes, I got a *great* deal, but I'm sure you could find similar here if you're patient.