Ascend actually used to offer speaker packages that included HSU subwoofers, before HSU started selling speakers. Nowadays Ascend has an arrangement with Rythmik. I think the Rythmiks would be great subwoofers too, but probably not be as good as VTF3 for home theater at the same price point. For musical detail though, I wouldn't doubt that they are better, and that is saying a lot given HSU's reputation for sound quality.
If you go with HSU, just ask for the enthusiast 2 package and upgrade the sub from the VTF2 to the VTF3, that is if you don't need all the speakers in the enthusiast 3 package. For whatever reason HSU doesn't have a five speaker package with the VTF3, but they will offer the same sort of discount if you ask.
Either one you pick, you will end up with a great speaker system.