1) Antec 900 is out of your budget for the 600 range. Stick with the 300 illusion.
2) WD is not doing so hot right now stick with the Samsung Spinpoint F3 or seagate 7200.12 they are using the 500 gb platters and you'll get better performance out of them.
3) That GPU is horrible if you are even thinking of comming close to playing games at max res.
4) Follow the guidelines in the sticky on how to request a build at the top of the page and more people would be willing to help.
hey what is a gpu