» Sat May 28, 2011 3:54 am
The right place to start is with a budget that includes both the upgrade video card and upgraded power supply that goes with it. Power supplies, even top grade ones, gradually deteriorate with age and use, losing approximately 10% of capacity a year. That is the reason that hobby builder folks such as myself will overspecify, getting 550 watts when 400 is actually adequate when new. Then, after the budget, tell us what the default screen resolution you will be using is, and last, (if there is leeway), how high of an image quality setting do you hope to get?
Today's Mainline Graphics cards, such as the HD 5670, can run on a 300 watt original equipment power supply that is still new, as can yesterday's Mainline cards, the Radeon HD 4670, and the Geforce GT 240. There has been no newer Mainline card from nVIDIA since that graphics card a year and a half ago. They haven't released any Fermi for that class (there is no 440), and their 450 and 460 cards do require more power than a stock power supply offers.
If you didn't have access to a place such as this forum, you would need to compare Graphics Card core speeds, VRAM speeds, number of shader units, and memory system bandwidths. The amount of VRAM attached is of little overall importance compared to those other factors.
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