I gave up trying to use XSI/Softimage, so I'm switching over to Blender, which by default can import and export .obj files (that's a start). Blender, if anyone wants to use it, is here: https://www.blender.org/
It can accomplish a lot of things and you can switch the user interface and controls to be more like XSI, or like Maya, or like 3DS Max. It's great. Also, there is an addon that I just installed that allows me to import and export .msh files!
Here is the link to the thread with the addon: http://orbiter-forum.com/showthread.php?t=18661
And just use Google to find any other addon that may be helpful for Blender users and post them here, if you would like!