If money isn't an issue, the sale priced HSU VTF3 MK4 would get my vote as well. For the extra output headroom mostly. Bass extension, sub 20hz output, with a single 12" in a medium sized room isn't really quantifiable imo, not as important. You're going to be impressed mostly by the output above 20hz, the midbass punch that you feel in your body in particular, and the HSU has gobs and gobs of it.
If you're listening at lower or medium volume levels you probably won't notice much of a difference between the three. It's when you crank it up the differences become more apparent. And If you crank, you want the HSU. IMO.