There is no video card that can deliver for this price. We can do much better than the 4200 by taking our 300 and seeing what we can get from THE LIST at THIS LINK:
http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107.html
But it's a shame you didn't reveal either the PSU in that machine or the make and model of the machine.
Bob
Ram : 8gb
Processor : AMD Phenom(tm) II X4 830 Processor 2.80Ghz
Current graphic card : ATI Radeon HD 4200
I am not really "computer hardware smart" but i do love to play a lot of online games and offline games.
I currently have a budget of about 300 bucks and im looking for the best possible graphics card for my system.
Im hoping i have enough money to get one that will allow me to run a good looking game like Assassins creed with all the settings on High with a 1920 x 1080 resolution.
Please be specific with your answers, i have no idea what to do D:!
Thanks.

Chowhound
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