My current room is tiny (10x12) but soon I'll be moving to a basement room. It's 13x21x7' with concrete floors/walls and 3 narrow windows. I have 1 SVS 20-39CSi and already I'm thirsting for more headroom in my small room. So moving to this larger room will definitely drop my SPL's. So here's what I could move to with my budget. 2 large sonotube enclosures each with a tempest and as much porting as needed. My front "stage" will hide the subs so they can be 6' high if needed and 20 or 24" diameter (lotsa volume). The amp is my current Samson S700 with 350 watts into each 4 ohm load and I'll probably just put both subs together to couple them. I also have an ART351 eq with adjustable highpass for a bit of subsonic filtering. I may switch to the BFD but dunno yet. Given that setup, what kind of SPL/extension can I expect? What size tubes would be sufficient, with what size port(s)? After having heard my friend's dual contrabass servodrive setup (dual subs, each with 2 12's and 2 15PRs), I'm ready for similarly insane bass. Note: Can't do an IB in this space, all the walls are cinderblock so there's nowhere to go.