Do you have a Microcenter nearby? It'll save you $50. Also, you should fill this out:
http://www.tomshardware.com/forum/261222-31-build-advice
My Build:
CPU: $125 i3-2100
Mobo: $80 Gigabyte H61 w/ two (16x/4x) PCI-e
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128482
RAM: $48 Geil 4GB (2x2GB) 1600CL8 DDR3
http://www.newegg.com/Product/Product.aspx?Item=N82E16820144436
HDD: $61 Samsung Spinpoint F3 1TB on Amazon.com
PSU: $40 Antec 520W Neo Eco
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371030&Tpk=520%20neo
DVD: $22 Any DVD Burner
Case: $40 Thermaltake V4 (or anything you like)
http://www.newegg.com/Product/Product.aspx?Item=N82E16811133179
Graphics: $150 Sapphire 5850
http://www.amazon.com/Sapphire-Radeon-PCI-Express-Graphics-100282XTREME/dp/B004W75ATI/ref=sr_1_1?ie=UTF8&s=electronics&qid=1304892899&sr=1-1
Total: $566
It's almost exactly the same as gengiskron's, but with two PCI-e slots.
520W should handle 5850's in crossfire if you upgrade down the road according to this:
http://extreme.outervision.com/PSUEngine
Notes: Double check that this mobo can do crossfire. It has two PCI-e slots but I'm not sure it can support it. I'd personally go for one of the G.Skill Newegg deals to get 8GB for $75 since you don't have the extra memory slots for an upgrade down the line.
EDIT: I sent a request email to Gigabyte to ask if the motherboard can run crossfire. I'll post the results when I get them. Emails are legally "published" documents, so you should be able to get a full refund even in 5 years if they say it's crossfire compatible, then isn't.