What on earth is he going to be using the 5770 for?
I don't see any integrated graphics on that card so I would say look into a decent radeon 4650 for anything you could want to do with it. If you end up needing a bit more power or DX11, get a radeon 5670. Both are powered right from the pci-e slot so don't need much power. You can find them for about $50 and $100 respectively.
The Q6600 is old and currently you can get a good yorkfield quad for $150
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115207
Buying parts from ebay and such is not something I would want to risk.
Edit: About overclocking. No one wants an unstable processor. Nor does anyone who overclocks want to go beyond the safe heat level. But make sure you do a lot of research beforehand. Guides and the such and pay attention to the safety precautions. If you overclock you might be looking to only do it a little bit - on stock voltage.