In the end I went for the more expensive RAM, simply because on my current system my poor RAM is the one thing that is really holding me back.Darg said:I'd never skimp on RAM. It's the main thing holding most overclocks back. Also you'd definitely notice the difference between 666mhz and 800mhz RAM at stock.
I also added a nice PSU (thanks for the Corsair recommendation), and a nice sound card as apparently it can make a big difference.