I actually have the Velodyne Impact 10 and the VX-11. The VX-11 is a older model but similar to the Velodyne Impact 10. I originally had the VX-11 that I bought for $140 in Amazon years back. I asked myself, do I get 2 new 12 inch subs, like the SVS PB2000, or just get another Velodyne? My room is twice as big as yours. I decided to get the Impact 10 on ebay for $100. Basically $240 for 2 subs that are 10 inches each. Let me tell you, using these 2 and EQing it, was a game changer. I know it only goes to around 30-35hz but it is more than enough for a room my size. Most movies and music don't go lower than 30hz anyways.
I already have dual Outlaw X12 subwoofers in my living room. I've even moved 1 outlaw to my bedroom to compare to the VX-11, and the only difference I heard was slightly better room shaking ability. When you play at moderate volumes in a smaller space, you really don't need a bigger subwoofer. I know reading reviews and online forums all talk about 15 inchers, 18 inchers but not in a small room with moderate volume. I don't do any bass boost either.
Get 2 Velodyne subwoofers and make sure you EQ it. I think EQing subwoofers is one of the most important things to do.
