Computer to run Sims 3 and all expansions

[RIDance]

I am looking to purchase a computer for my son that will run the Sims 3 and all of the expansions. Please point me in the right direction!

[whiterider]

http://www.modthesims.info/showthread.php?t=330413 <- Have a read through that, and do some research. Once you've got an idea of where you're going, feel free to post specific questions (e.g. which of a handful of components you're considering is better), along with your budget. :)