I just purchased a Gateway DX4320-04e. It came with a 300W power supply and an ATI HD5450 graphics card. I just purchased a Sapphire ATI 5770 1G and would like to know what power supply I should upgrade to, or if I need to at all.
well i don't know wether gateway uses standard atx-psus or not, so that might be a problem. If it is a normal atx psu then it would be very simple to change it.
You'd need a good quality 500-600W unit to run it with nice margins for comfort. The system will use around 300W under heavy load, so you would be maxing out the stock psu. I don't suppose you can overclock it, since oem rigs tend to have their BIOSes locked up thight (overclocking an X6 will increase the power consumption (and performance) quite a lot)
you only really need a good 300-350w unit for a 5770. im not sure how good the gateway unit would be, but i would swap it out for somethng in the 400w+ range from a good psu maker like seasonic, corsair, antec etc. a good 450w antec PSU will set you back less than $50, that is what i would go for.
a 450w antec is about $50 while a 600w unit is near $80, that is a big enough diff in price to go with a 450w unit that can power a 6850 quite easily. I dont think the guy is going for a gtx480 or anything.....