Regarding the .ASE format, it is a 3ds max proprietary file type. No model conversion program can create it... Deep Exploration, dotXSI, Crossroads 3D, PolyTrans, they all do not have support for it.
And even though there is support for 3ds obj, etc in the toolkit, there really isnt because 1) it is not fully supported, 2) the link to download them is broken.
I think that there should be a common interface to import 3d models in xith and there should be support for the .x file format. It can be converted in those programs so it is accessable, whereas one must have 3ds max in order to use Xith right now...