I've had a 3/3 for about six years and I liked it enough that I looked right back to HSU for an upgrade. Initially I thought I may just use the 15H, but am now planning to use them together if it will be a good combination. I already have both subwoofers here, but have yet to test 15H. I had been running the 3/3 with both ports open.
Placement is likely going to be limited to the front wall (one placed between the left tower and center channel and the other between center and right tower). As I've built a small sand filled stage that is about 2" high and wrapped in velvet, I'd prefer to not have to do an excessive amount of pulling them for tuning changes if I could get an estimation of a setting combination that would work well for these subs. Primary use will be movies and games.
The front wall is about 11' (though most of the room is closer to 11.5'), room depth is about 18' and ceilings are 8' . Front row listening position will be about 11' behind the front wall (12" riser behind for the second row).
Thanks for any suggestions