Hi I'm using a Velodyne SPL 800 Ultra along with my PMC GB1 and DB1+ speakers and they sound fantastic together, however I've got this idea in mind and would appreciate any advice. The Velodyne Sub Frequency Response is :16 - 240Hz (Overall) 26 - 120Hz (+/- 3dB). Do you think I would gain anything by adding something like a BK Monolith DF which has a frequency response of 20 - 120Hz (+/- 3dB), which apparently can go as low as 15Hz in room? I'd be setting the Monoliths Low Pass Crossover at 40Hz and leave my Velodyne's at 80Hz. My room is 3.5 x 5.5 meters with Tv on 3.5 wall and velodyne inside front left mains. I sit facing TV (Samsung PS59D6900) about 3.5 metres from screen. The floor is concrete covered by laminate. I'm in a ground floor flat in a block of four with two ground and two first floor.