That is a great build. E8400 is an awesome chip, better value for money for gaming as very few games use quad core. I would go for a gigabyte motherboard, they are cheap in comparison to asus and can overclock well.
This will do fine: Gigabyte GA-P35-S3G iP35
Motherboards have very little effect on performance, this board will allow you to get the E8400 to 4ghz and will safe you some money.
The antec 300
imo is the best budget case. You can't gto wrong with that. Great air flow.
Also, if you are wanting to play some older games, they will not work on 64bit vista. I'd advise getting 32bit.