Hey, I put together a complete PC for you that comes with all the specs you want right on budget.
All the parts are from Canada Computers and you can see them online. (Some are currently on sale so the total build is $30 less right now than usual).
If you pick it up at a store there's no shipping charge of $10.
Use Linux (Ubuntu is popular) for your operating system, it's free and you can do what you need it to.
Motherboard - MSI B75MA-E33 $49.99 (59.99reg)
CPU - Intel Core i3-3220 Dual-Core $114.99 (124.99reg)
RAM - 4GB (2x2GB) Kingston HyperX Blu 1333MHz $24.99
HDD - HGST Deskstar 500GB $59.99 (64.99reg)
Optical Drive - ASUS DRW-24B1ST $16.99 (19.99reg)
Case - Cooler Master TC-102 Mid ATX HD Audio w/500W PSU $42.99
Tax: $40.29Total: $350.23
Let me know what you think