I'm having a heck of a time comparing benchmarks between these 2. I don't expect anyone to know for the machines released today, but if you could give me a hint with regards to the previous highest end iMac model. My assumption is I will notice a big speed increase...correct? I spend most of my life in CS3, soon to be CS4. Any video processing I do is incidental and not important to my decision. My 4 gigs of ram seems to be enough for me. I don't play games on my mac.