i would get the Zalman CNPS7000A-AlCu variant. it is cheaper than the Zalman CNPS7000A-Cu because it is made from aluminum and copper (copper is more expensive than aluminum and is harder to work with). both coolers cool very well and keep the cpu at about the same temperature.
the "AlCu" that i bought was $35 USD. i think the "Cu" is about $10 more. the "AlCu" is also lighter than the the "Cu." so if you move your PC around a lot, you do not have to be so careful with the "AlCu" as the "Cu."
just make sure you go the Zalman web site and look at their motherboard compatibility list. as you can see from didou's pic of the Zalman, it is large so the heatsink does not fit all motherboards.
IMO both the Zalman CNPS7000A-AlCu and Zalman CNPS7000A-Cu excel at keeping the cpu cool at low fan speeds. set the fan speed at about 7V (which is about half way with the included fanmate) and it is inaudiable. even with the fan at 12V, it is quieter than a lot of other cpu fans and cools very well too. i strongly recommend that you consider the Zalman.