I want the Best Graphic card for My a8n-e motherboard amd athlon 64 Processor 300 1.81ghz 2,00 gig ram i currently have a nvidia 6600 installed and and to upgrade to a 100- 120 Graphic card
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On a system that old, I probably wouldn't put any more money into it and start saving for a new system. Anything much higher than what you currently have is going to start being held back by your single core CPU.
You could pick up a cheap HD4650/70 card and stick in there. They would be a huge improvement over your 6600. Anything more powerful would not be able to run at its potential.