I don't really understand the videocard.
If you're going for budget, why not go for the HD 2600XT?
This card is rat sh it for gaming... the 7900GS will sh it all over it. Ive got one and it still runs most games well including Bioshock at 1366x768 on my 42" LCD .
I dont know how you got that deal but the 7900GT and the 1950 series is worth a look both a still excellent DX9 performers.
Good choices all up the only thing i would consider would be a cpu cooling option... something 120mm fan based will be quiet and get a good OC. Thermalright 120 Ultra Extreme, make sure you get a fan for it though cause it dont come with one.
Case: buy locally. Shipping always kills any savings. Shoot, many people have old PCs with perfectly good cases that they throw out.
Memory ^^^ what zenmaster said. The key to overclocking and stability in ram is wide voltage ranges. A little difference in speed isn't even more than a couple of FPS, if that(the bottleneck is sill the bus with modern memory) Geil also makes memory like this for a bit more money. (IIRC, newegg had some with a $30 rebate last I checked)
That leaves the video card. Get the 7900 GS used for $100 or less.
Well if I can get the crucial memory that's better and would work if I undervolt it to 2.1 why get the a-data? they're the same price and from what I've heard the crucial ballistix are extremely good ram. The case has free shipping