Which Liquid cooling for my Zalman GT1000?

Hey I am going to do a major upgrade with my computer im taking everything out except the hard drives and keeping my Zalman GT1000 case and going to get an Asus Rampage II Extreme, Core i7 920, 6 GB of DDR3 triple channel (3x2GB) and a 295GTX and either Corsair TX-850 or zalman ZM850-HP psu. However the problem I am having is deciding which cooling to get cause im either thinking of getting air cooler ( the new Zalman CNPS9900LED) or liquid cooling. I would much prefer liquid cooling however not sure which one would work best with my case (cause I would prefer the radiator to mounted on the exhaust fan) however not sure which liquid cooling system would be the best, and considering how much I am paying already for the upgrade (around 4k) I don't mind how much the liquid will cost as long as its not over $500.

If anyone has ideas on which liquid cooling to get that would be very helpful. Thank you!

Only the cpu

A DIY loop will offer the best price/performance.

~$70 Swiftech MCP355 or MCP655 pump
~$90 Thermochill PA120.2 or ~$60 Swiftech MCR220
~$65 D-Tek Fuzionv2 CPU block
~$20 Swiftech Res
~$20 ~10ft MasterKleer 7/16" id Tubing
~$15 for 1/2" barbs
~$8 Silver Kill coil or $3 PT Nuke
~$5 5gal Distilled water

I have found out i can get a 120mm radiator from thermochill and place that on the rear of the case where the exhuast is. However will one radiator be enough to make it worth getting a liquid cooling set or should i just get a good air cooled fan, hoping to get the core i7 to about 4Ghz and ive read that its possible on air cooled however gets close to 90 degrees on load :O

so is it worth getting a liquid cooling system if im just going to have 1 120mm raditor or should i just get the new zalman CNS9900 or TRUE 120?