The SK6 is a great heatsink, I am running run on my TBird 1.4 @ 1.5 (or 1.6, haven't decided yet) but even at 1.6 with 1.95V the temp stays below 55C. With a Delta fan fitted and a closed case the highest I saw was 50C. I am running at 1.5Ghz now though, with a quiter 27CFM YSTech fan.