If you can afford it get Lightwave. Then add Poser 4 and the Pro Pack which has a Lightwave plug in. Last but not least, get Ozone 2.0, the Vue D'Esprit plug-in for Lightwave. Well, you did say you would be able to purchase any and all the software. :-))

Ideally run the whole lot on a G4 Mac under OS.X

More realistically...
I use a dual PIII 1Ghz box with 1Gb RAM running
Paint Shop Pro for 2D stuff (highly underrated it is too)
Amapi 6 for modelling (now on offer for 149GBP in the UK)
Poser 4 and the Pro Pack for people
Vue D'Esprit for rendering

Whatever you get, have fun with it!
Mark