Hiya.
The *only* success I've had is exporting as .x from XSI. It saves objects and animations. Then import into UltimateUnwrap3D for UV'ing. Texture in Painter 9.5. Save as DirectX v8. Import into MED. Kill the bones and save as 'vertex animation' in MD7 format.
For some reason, MED will 'ignore' the last (or is it the first?) bone of every chain; so if you have a 3-bone chain, when you open in MED and show bones, you will only see 2.