Since you are looking to optimize for one main listening position, and since you have a large volume of space to fill, it definitely does make some sense to start with one very large and powerful subwoofer such as VTF-15H.
Any chance that you can place a pair of HB-1 MK2 on speaker stands (with tweeter close to your ear level when sitting down), located to the immediate left and right hand side of the TV?
Note that the HB-1 MK2 needs a minimum of 1-2 inches of space behind the speaker. So a side-clamping wall mount is acceptable. But for critical 2-channel listening, it is nice to be able to put them on stands and pull them away from side and back walls in order to reduce the amount of reflected sound energy.
Pete - Hsu Research