There is a Sony model, I think wm40 that was recommended to me by some of the fine people on this board. I have yet to purchase it though, so I can't tell you how it sounds.
Yes, it is the SA-WM40, can be found on Yahoo Shopping for as low as $138, average price is around $150, B&M prices typically $199. A bit boomy, but a good sub at this price.
The audiosource and the sony are probably going to be your best bang for the buck if your budget is $150. I first started with a Audiosource SW15 and boy was that thing big. I liked at first but then after awhile it became just too boomy and bloated even after I put in some polyfill. I since upgraded to to an SVS sub and have never been happier. Nice smooth and deep bass
I second the Sony mw40. I've had it for about 3 months, and yes, it is a little boomy, but what do you expect for around $150. It's still a great sub, can't be beat for the money.