The challenge is how far you can go in the customization. At the end, SobiPro has a full SDK, supporting Joomla 1.5, 2.5 and 3.0.
I use to work with other directory extensions. They are no match for top-directory requirements (mostly oriented to a single catalog or simpler structures).
The last version, SobiPro v1.1 shows how easily can accomodate Bootstrap and J3, in the same package with a stable solution.