Yes, as TheWingedOne said - Universal Binary. this means the program is optimised for Intel Macs. And indeed an incredible step forwards in performance. And i mean a really BIG step forward.

Memory i think is ok on your machine, the two graphic cards i question a little. Is this really necessary? I was unsure in this field as well and thought the same. Then i found out that the default NVidia board that is build in has already 256 MB and is able to drive two monitors without a problem. Now for rendering processor performance is key, not graphic card quality. I at the moment have a new 20“ TTF monitor as working monitor and my old 17" moinitor as second here. Is perfect for my needs.

One day your ship comes in - but you're at the airport.