I've already done the HS mod. There's no need for a fan on the northbridge. The heatsink is plenty. The underside of the board doesn't even get warm.
I've ruled out the power supply, I borrowed a 550W Q-Tec supply from somebody. That should be more than enough to suit that system. Bluescreened within minutes of bootup.
I'm going to swap the ram with some PC2700 tomorrow and see how it goes.