Wow! Awesome advice!!!
I use maya for character animation - My scenes never have more than 2 active rigs (90% of the time just 1 rig) In terms of size and mesh density the rigs that I use are almost exactly the same as the free ones at:
animschool AnimSchool - Online School for the 3D Animation Field
Free Animation Rig | Animation Mentor
Would it make sense to get 2 cheaper cards and run them together?
(I'm not sure if maya can do that)
I hardly ever do any rendering, so I only use the playblast feature because I don't take care of the lighting or anything like that. (this just renders the viewport)
The most important for me is viewport feedback speed when moving stuff and the general responsiveness of maya. (I don't use viewport 2.0 although I suppose it is faster - my current card doesn't support it)
EDIT: I have found a used nvidia quadro 600 (not a k600) for about 70$ so i might lump for that and then if need be get some more ram and upgrade to a quad core. What do you think??