CURRENT GPU AND POWER SUPPLY: (e.g., ATI Radeon HD 4850 and Corsair 750TX 750W PSU - without this info, it's really hard to help you)
OTHER RELEVANT SYSTEM SPECS: (e.g., make/model of CPU, MoBo, memory - this can help us determine whether or not a given card is compatible with and makes sense for your system. For high-end cards, knowing your case/cooling setup may also be helpful)
PREFERRED WEBSITE(S) FOR PARTS: Tigerdirect.com or Newegg.com
COUNTRY OF ORIGIN: USA
PARTS PREFERENCES: My HP Solution Center says that I have to use one of the following options for Graphics Card: Must select one of the following options:
Intel Graphics Media Accelerator HD
GeForce 405 (1 GB)
GeForce GT420 (2 GB)
GeForce GT520 (1 GB)
GeForce GT530 (2 GB)
Radeon HD 6450 (512 MB)
Radeon HD 6450 (1 GB)
Radeon HD 6570 (1 GB) single bracket; DVI, HDMI, & VGA via adapter
Radeon HD 6570 (1 GB) single bracket; DVI, HDMI, DP & VGA via adapter
OVERCLOCKING: Maybe, I need to understand what this is...
With your 300watt PSU the best choices are from the most powerful HD7750, HD6670 and HD6570 all will run on a 300watt modern PSU. With a PSU upgrade you have more options if your case is not a small form factor.