Sunfire excels at making very small subwoofers that are great for their size. However, if you don't need one to be that small, you can get better performance for the same amount of money (or less money) from other companies like SVS.
I recommend avoiding Sunfire subwoofers unless you absolutely cannot have a large subwoofer. If you absolutely must have a tiny subwoofer, then they would be at or near the top of the list.