All of the rooms I have seen with "glorious" sound have had vaulted ceilings, although there could be a bit of a placebo effect going on (I'm tall and slightly claustrophobic).
If the ceiling is going to be at a 45 degree angle (eg 12/12 pitch roof or similar) or even close I might stay away from it though, since a 45 degree vaulted ceiling introduces some of the same effects as a square room. Your use of ^ concerned me because that looks awfully like 45 degrees
The vaulted ceiling would take your room volume up from ~3600 ft^3 to ~5200 ft^3 which probably is enough to affect how much your sub can pressurize the room, but on the other hand the Axiom DSP subs can probably handle the extra volume more gracefully than most.
Did your username come from the band (one of my all time favorites), or from somewhere else ?
