Sonnie:
I understand, it would be a lot more work.
Should I ever have the opportunity to build a purpose built home theater I have always envisioned using the platform for my sub(s). Living in S. Florida, we don't have basements, and attics are very hot most of the year, so IB's are fairly impractical. SAF dictates unobtrusive, plus I hate to waste space.
It's a shame you weren't just building the room
Paul