Well, don't I feel like a sucker.
I built a new Haswell box since my old computer was positively ancient. I built it with the explicit intention of using both virtualization and maybe even trying out TSX. Imagine my surprise when, just after the CPU return period expired, I realized that the top of the line processor doesn't have all of the features enabled!
Paying the extra for a K-series product also means giving up support for one of Haswell's key features, the TSX extensions that enable transactional memory. Intel has stripped out the VT-d device virtualization and vPro management features in the K series, as well.
In the end, enthusiasts face a rather unfortunate set of choices in Intel's Haswell-based product offerings. We can't help but think this situation wouldn't exist if AMD were putting more competitive pressure on Intel.
Is this some sort of a "soft" limitation that could be overridden, whether by microcode or BIOS etc, or is there no way to enable them on these very expensive CPUs?