Dude,
I spent appx 700$ usd on mine, before i modded my case.
I have a AMD Athlon X4 2.8 gig processor.
Nvidia GTS 250 1 gig video card, 6 gigs of ddr3 ram ( Kingston 1066 i believe it was ) ( going to get 2 more gigs eventually)
running it all on a MSI 770-G45 mobo. Has 4 easy OC settings if you're into that sort of thing, where the Motherboard will set the computer up to overclock the cpu it you wish it, though i see no need wiht the current setup i have.
and I currently have a 650 watt power supply, though i am going to get a 800 watt modular psu soon and use this one a sa switched Desktop psu for Desk lighting issues. ( don't ask, i am heavy into modding everything. )

I am not a renderer by any means, but i know my old rig used to take about 1.5 hours to render one scene i had, with fg for lighting, now it renders in about 10 minutes,

also, Opened a model once, just to see how far i could push the card, and stared to subdivide it.. I was running over 2.5 million polys at 20 fps according to maya hud with no lag issues at all, and got tired of trying to lag it out.

And it calculates dynamics in a snap ( so far as i've tried anyway, and my old rig used to lag out and crash on the things i am doing now.)
The only thing i would change on my setup so far not mentioned above, is i would get AMD's Phenom II 3.5 Gig Quad core processor, the one with the 6 meg and 4 meg l3 cache .. that bad boy is lightning fast.

My advice, build my system save a crap load of money and still get 2011.
F.Y.I.
i could upgrade my psu, get the new CPU and also the extra 2 gigs of ram and spend just under 400$ to do it all, so even that is well within your price range.

g-man