The SLK 'sinks are good, but too narrow to make the most out of a large (quiet) fan. I have the SLK900U and saw no improvement moving from a 2600RPm 80mm fan to a 2800RPM 92mm fan. It turned out that the optimal performance/noise tradeoff (for ~2-2.5Ghz) seems be an 80mm fan @ 2600RPM.
IMHO, best bang for the buck that's also quiet is an AX-7 with a 92mm fan on it. Use whatever you want to adapt the 'sink to a 92mm fan... common/cheap metal household wiring straps will work if you only want to drill a hole, not fab an entire adapter-plate. Of course it's up to you to choose the right fan or throttle it as needed.