For that style of music T36 should work great. BTW, There is a considerable difference between MSRP and actual cost on Growlers, that's very impressive if you can get 2 T36 for the cost of 1 Growler. Les must really like Josh. That's an almost stupidly good deal.
Anyway, I'm not looking for some sort of debate, I built some Titans myself and they work fine with my B rig. They have lots of output. If Josh has already heard T36 and is happy with their sound, that's perfect, and did I already say A GREAT PRICE!
I guess a lot of my comments re T36 are moot since I have not heard that particular Tuba model.
Re the Titans, I think Wayne is being pretty modest in his comments here. I don't think 2 Titans = 1 12Pi.... close maybe in some respects, but very different in low end extension and especially in distortion. Also from my experience of Labs there is a noticeable difference in perceived "sound" vs Titans, regardless of measurements. I do prefer the "sound" of a lab (and I presume 12Pi should only be an improvement on this). I am by no means a fanboy of Wayne, Tom Danley, Bill Fitz, or others. Each has found a good niche, and their designs in some respect are driven by their end user group.
Take the weight and size of subs into consideration.... Bill Fitz's subs are typically significantly lighter than others... many BFM builders don't have a crew to haul heavy gear in. But that comes with a penalty. I really doubt that Wayne and Tom D are completely oblivious to the fact that their subs are typically much heavier and in some cases larger than Bill's.
I know I would not put my Titans on a truck and send them out on a national tour, they would likely get very beaten up and I wouldn't trust the 3015LF to survive so much abuse (I like the 3015LF, but even though I have never had one fail, I still have a hard time trusting it and am very careful with them). That's fine though, it's usually ME running them, and so they don't get abused.
Anyway, again I have no issue here, these are all VERY good subs we are talking about. I have no intention to discredit any of them, they all fit a niche and are in many cases considerably better than many commercial offerings. I did not mean to open up a can of worms.
Josh, the T36 should work very well for you.