Basically -- a gaming machine is a good 3d Modelling machine. Lots of RAM, lots of HD-space, fast processor, and a decent-enough videocard (note: 7800-series cannot NVStrap to Quadros as of yet... at least not the cards released on the 7X00-line thusfar)
Obviously -- the only real thing you're dependant on is how many polygons you wish to display, how often you want to go without clearing history, and how long you wish to render.
If you can wait a few extra minutes... then save the bucks.
(If you wish to give us your city we might be able to scan for local computer resellers for you -- ones which look legit. If you're nervous about it -- I live in Kingston, Ontario, Canada... ... yes the town with the big arse Supermax prison... no I do not go there :p (Though I did walk through the nearby University campus.)