I have the budget of $ 500 to upgrade my audio system, I have a very good 12 inch velodyne, but I want to buy a new one. And I have 2 options. the first is to buy one and join it with my velodyne, and the second is to buy the subwoofer and discard the velodyne. Now, the 2 options to buy a subwoofer that I have in mind are these two. Rythmik L12 sealed 18-100hz +/- 3db (servo subwoofer) SVS PB12 vented 18-150hz +/- 3db