Right now I have a 15" flat panel iMac 800mhz with 512 MB RAM (via two dimms at 256 each). I'm thinking about leaving one of the 256's and replacing the other with a 512, thus leaving me with 768 MB RAM. Would I really notice much difference in anything? I use my computer pretty heavily with film editing and such. Is the change with the $150 at crucial? And would there be any issues with one dimm being apple and the other being crucial? Any responses would be greatly appreciated. Thanks.