10A on the 12v rail is 120W, which is pretty sad if it's only one rail. At load, the HD 3850 seems to draw between 80-100W (well I think 98 is worst case), which doesn't leave much for your CPU and everything else. I doubt your PSU could even sustain the 10A on the 12v rail. I say no. Get a decent PSU if you want to upgrade your GPU. Is it even worth it for your system? What are you full specs?