If you want to get the most bang for your buck try looking at some refurbished laptop that you can find online. Here's one from newegg.com.
http://www.newegg.com/Product/Produc...82E16834300021
Price: $280 USD
Intel i3 330UM
2GB ram
250gb HD
Windows 7
It will do pretty much everything you want and if you ever need to speed it up you can always drop some more ram into it for a few bucks down the line. I checked and you an grab 8gb of memory for this thing for about $60.
Don't be scared by the refurbished tag. I've owned a lot of refurbished items in the past. They all go through the same testing process as new devices. In fact they go through the testing more often than new devices due to the fact that if they are a repair item they need to test it once to see what the problem is then test it again to see if the problem is fixed. A lot of "refurbished" items are also overstocks sent back to the manufacturer. They take them out, test to see they are working, slap a refurbished label on them and sell them for cheap.