You’ll need the extra processing power for your compressed codecs, Apple Pro Rez, DVCProHD. If you’re working with the Media 100 HD codec, or a mix of compressed and uncompressed codecs then you should be fine with the dual core systems, 2, 2.6, 3Ghz systems.
The 42-ES, and the G-speed should work very well for you.
Scott
Media 100/Boris Fx