For $50, I would recommend you to go for 4650 HD.
Good performance at 1280x1024, meaning you can maximize settings in most of the games including Dragon Age
For $65, I would recommend you to go for 4670 HD.
Good performance at 1680x1050, meaning you can maximize settings in most of the games including Dragon Age.
If you go for 4650 HD, you won't need to change your PSU.
If you go for 4670 HD, I think you won't be safe with 300W PSU
Forget about GT 240,
A 9800 GT for $90 will be great choice but then again your PSU ....
For PSU here is a recommendation:http://www.newegg.com/Product/Product.aspx?Item=N82E16817371016http://www.newegg.com/Product/Product.aspx?Item=N82E16817139008
Both are excellent choices at the price point.
And will be good for any future CPU, Motherboard e.t.c. upgrades.
If you don't have the money yet, Dont make a stupid decision,
Wait a while, gather some money and then go for either of those PSU's and a 4670HD or may be 9800 GT
I would strongly recommend you to wait a bit if you don't have the money to those yet, but if you go with 4650, you won't need a new PSU