Manufacturer websites are unreliable guides on psu guidelines. I had found that the video card manufacturer recommendations to be arbitrary and wrong at times. In the case of the 7600gt, the 300W recommendation is arbitrary because there are practically no psus below 300W these days and anything lower is probably not atx12v compliant.
Since the 7600gt consumes only half the power of the x850xt and power supplies degrade over time, the 7600gt is a prudent choice.
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