After much thought and feedback (thanks to all), I reckon I'll go with the Scythe Mugen 2 and use a one year-old unopened tube of Arctic Silver 5 thermal paste to mate it with the i7 920 which I'll be overclocking to a fairly conservative 3.66Ghz. Does AS 5 go stale or out of date?
If the paste is still a paste I would imagine it would be fine (If it hasn't dried up and gone hard). The new cooler will come with paste as well though (unless it's OEM), so you should be fine. Good luck
I have the Zalman 7700-Cu, pure copper with the FanMate 2 Speed regulator and it's realy nice. Stealth and Cool, compatible with all Cpu.