Upgrade advice

Currently

- Thermaltake Purepower 600.
- MSI P43-C51 LGA 775 Intel P43 ATX Intel Motherboard
- Intel Core 2 Duo E8500 Wolfdale 3.16GHz LGA 775 65W Dual-Core Processor
- 4gb DDR3 1333 / PC3 10666
- Radeon 4770

Looking to upgrade to be able to play BF3. I'm on on the fence about how much I want to spend in a $300-700 range. Will upgrading the video card alone allow me to achieve a good frame rate on high settings? Any advice and product suggestions would be much appreciated.

Thanks in advance!