My q9550 is running at 3.58 (on stock cooling and the voltage is around 1.264-1.275) DDR2 pc6400 Patriot LLK 4 gig kit at 421 mem speed, Asus P5K-e Wifi Mobo Syste, FSB = 1684 for total of 3.580 ghz.
Mem will do much faster but i havnt messed with it since swapping out my conroe e6750 (stable...