This would be more than enough for your needs. I would not recommend a $500 build as you will be cutting too many corners at that point. Includes an SSD and Windows 8.1 as it is cheaper.
| Link | Parts (from TigerDirect) | Price |
|---|---|---|
| Link | Intel Core i5-4440 | $179.99 |
| Link | ASUS H81M-E Micro-ATX | $59.99 |
| Link | Kingston HyperX Fury Blue 8GB (2x4GB) | $63.99 |
| Link | Crucial MX100 SSD 128GB | $74.99 |
| Link | WD Blue 1 TB HDD | $59.99 |
| Link | Sapphire Radeon R7 260X 2GB | $109.99 |
| Link | Corsair CX430M | $29.99 |
| Link | Cooler Master N400 Mini Tower | $59.99 |
| Link | Windows 8.1 | $89.99 |
| Subtotal | $768.91 | |
| Minus Mail In Rebates | -$40.00 | |
| Total | $728.91 |