Currently Sims 3 is having massive problems with newer cards, but everyone listing a Nvid 8800 GT model seems to be playing fine - although even with a HD 4890 from Radeon - I cannot play with full Graphics setting without lag and stutters.....
Seems to be my OS, as well as new GPU problem - and possibly Game needing patched.
I know that's not a lot of help, but it needs to be said - if you haven't bought Sims3 yet - I'd hold out for a bit- until some patches are made to fix the too common issues of lag, stuttering, and crashing that seem to effect 9/10 of the players currently.
Although I must say, it's pretty rediculously fun even though I stutter in game play... the customization and colours are.... amazing... you can color your roots, main hair, highlights, and tips for just the right hair color you want.... which is.. supurbly detailed. The new system is pretty easy too, and... it's just freakin amazing. Lol!
IF you liked sims, loved sims2, you'll die for 3. Speakin of death - you can now avoid death with special flowers! and gardening (and other misc skills) actually work! you can have your own food supplies all the time! and death got better looking.... and ghosts look AMAZING. Although you can no longer drown your sim with just a pool... they can climb out the sides without a ladder - but you can add walls to prevent that... hehehe... DIE SIM DIE!
I hope someone else has some better input on the Quality Graphics for Cheapest price for ya... I started to ramble... sorry.. hehe.