Heatsink Advice wanted

[Zureal]

I currently have the Arctic Cooling 7 heatsink and would love to overclock my CPU close to 4ghz stably. Do you think my current heatsink is good enuf? If not then what would be better? I would like to stay with Air cooling but I am not against a water cooled CPU if i have to. One of the things I love about the Arctic Cooling 7 is how utterly quiet it is, so if i could stay that way or close to id love it

Current Build:
Win XP SP3 <Planning on replacing with Win 7 Ultimate 64-Bit >
M2N-32 SLI Deluxe Edition Motherboard (Wireless Edition) <Planning on replacing with AM2+ gaming board of somesort :/ )
AMD Phenom II 940
2 GB G-Skill Ram < Planning on replacing with 8 GB Ram >
2x XFX Radeon HD 5870 XXX Edition
2x 320 GB Western Digital HD < Planning to replace with a 1 TB Unit >
Creative FX Gamers Edition Sound Card
750 Watt CoolMaster PS < Planning on replacing with a 1000 Watt Unit >
Samsung DVD-RW
Thermaltake Element G Case

[Atomic Rooster]

This will do the job nicely without breaking the bank: XIGMATEK HDT-RS1283


if you really want to go nuts, these are considered one of, if not the best, air coolers available: Thermalright TRUE Copper Ultra-120 eXtreme

[Cabbs]

If you grab a TRUE copper, find a way to give it extra support. Those suckers are heavy.

I'd also look into the Prolimatech Megahalems and the Noctua NH-D14 for top-performing heatsinks.