Yeah there should be a noticable difference. The difference between DDR1 and 2 is really tiny, its a price saving thing more than anything else, DDR was always good with AMD hard to improve on, DDR1 wasnt as good with intel but AMDs memory controller was so good it took advantage of lower timings that intel couldnt so they went for DDR2 with the better memory bandwidth, AMd went with DDR2 eventually primarily because if price its cheaper to manufacture than DDR they gained pretty much 0 performance over 939 systems from switching to DDR2 memory.
I would check out the temps first before buying anything unless you were planning on it allready.
well heres the thing i have been lookin to boost the mem on it for a while the sticks i have in there are over 2 years old now and once back in the day over clocked with the old computer. I have been looking around reading up on site but i could never find anything that proves to be the better buy for mem but since i have seen alot of people suggest corsair i think im might try em out but once i get home to night ill run that program and see