If you have combustion already, the likely candidate for your 3D stuff is MAX 4. As mentioned in the earlier post, these two packages are tightly integrated. Max has a very hot 3D tracker. Besides the obvious, Max 4 has come a long way with it's IK system, not to mention the new skinning / enveloping. You can also choose to use other renderers (for an extra cost) such as Pixar's Renderman, Mental Images' Mental Ray, BMRT as well as the new powerful renderer Brazil Rendering System by Splutter Fish.
MAX's price point ($3500) is very attractive for a start up shop and it is an easy all around type of program, especially if you have to do a lot of different stuff.
Take a close look at Houdini, if the $18K price tag is in your budget, and you have a good handle on their methodology, buy it.
hope this helps,
Good Luck
b