They are. @ ThunderSnake : your best bet is Blender as it's got the most fully featured MD3 import/export scripts now, mainly down to the extended work the guys on the Open Arena project have put into it. I've got some legacy info on my tools page here, but you'll be directed to the AO wiki anyway.
and of course the classic freeware app blender,- I am sure that many specific quake3 plugins are already available as pyton script for it. XSI is a graet package,- but I am somewhat doubt that it has all the export/ import support oter famous packages for gamedev have. Perhaps you need to run some xtra tools to get it into…