Mox I guess xsi foundation is most accessible price wise of the high end apps and I guess it depends what is going to be usefull to you. If you are wanting to do hair and cloth then eventually you will need to shell out big bucks. I have no idea which of these big softs are best, I not own any, but what ever you buy is big investment in training and time. Maybe trial the learning editions to see if they suit what you want to do. If you want to make 'lord of the rings' or 'ice age' might require different capabilities, and it wont stop there. You need compositing and camera tracking software etc etc, whole studio, 50 animators and render farm
If it is to make VFX, advertising or 3dstills or get work in the industry maybe something different again, so maybe a clear vision of your endgame is paramount before shelling out the dollari.
Not much help I know, I am wrestling with this myself at moment, I just beginner. Here are some of the things I thinking about -- Have not mastered C5 yet, but no confidence in daz intentions for C6. Render quality. Can I learn and drive software myself without serious programming skills. User base ( I think 70% maya and 3ds?) Does software have industry proven track record and future. Software tools and feature set. Where do I want to be in 5 years time. Would learning this software give me marketable skills. What advances will there be in next 5 years which mean I not have to learn to do this complicated stuff
Price. Personally I think XSI foundation is next step for me for pricewise but I feel maya beckening seductively longterm, and maybe its wiser and cheaper longterm to jump into that.
I take on board what professionals say here sometimes too, 'whatever tool gets the job done'