Assuming, for the moment, that you are just intending to cool the CPU, You need to decide if you are bound by a budget. For the low cost solution, there are premade kits such as those offerred by Vantec and Thermaltake. Since the Core 2 Duo does not consume as much energy as the previous Prescott procs you know it won't produce as much heat either. Given that, if you are limited in funds then the BigWater kit would probably suffice. However, as I am not a very big fan of such kits, I only offer it as one possiblity for you. In this area, premade kits will, generally, cost between $80 - $150.
There are kits offerred by manufacturers which are comprised of much higher quality equiptment like those offerred by Swiftech and Danger Den. However, those kits are more expensive and you would be loath to find one less than $200.
Ultimately, if watercooling is your cooling solution of choice than you will find that Do-It-Yourself (D.I.Y.) is where you will end up. It is more expensive, although a basic kit in this area (for just cooling the CPU) will cost about as much as the specialty kits offerred by Swiftech and Danger Den. The difference in DIY is that you will probably end up using a cross section of equiptment from a multitude of companies like a pump and waterblock from Swiftech, Reservoir from Danger Den, tubing from Tygon, etc.
The setup will, most likely be:
Reservoir - pump - CPU waterblock - radiator - reservoir
You'll need the following equiptment:
Tubing, clamps, CPU waterblock, Reservoir, pump, radiator, cooling liquid, coolsleeves (optional)
Tubing:
Tygon 1/2in. ID 11/16in. OD Laboratory Tubing #R3603 (10ft) $22.50
http://www.sidewindercomputers.com/ty1idx11odx3.html
Clamps:
Breeze Miniature Hose Clamp 7/16 in. to 25/32 in. (10) $3.60
http://www.sidewindercomputers.com/brmihocl7int1.html
CPU Waterblock:
Swiftech STORM Rev 2 Universal High Performance block $80
http://www.sidewindercomputers.com/swstunhipebl.html
OR
Swiftech Apogee Extreme Performance block $50
http://www.sidewindercomputers.com/swapexpebl.html
Reservoir
Danger Den Single 5 1/4" Bay Reservoir $30
http://www.dangerdenstore.com/home.php?cat=27
*This is meerly one type of reservoir. Your taste may very here
Pump:
Swiftech MCP655 12v DC Pump $77
http://www.sidewindercomputers.com/swmc12vdcpu.html
Radiator:
Black Ice XtremeII Radiator (dual 120mm) $43
http://www.dangerdenstore.com/product.php?productid=199&cat=85&page=1
OR
Black Ice Xtreme Radiator (single 120mm) $33
http://www.dangerdenstore.com/product.php?productid=1&cat=85&page=1
Coolant:
Primochill ICE (nonconductive) $20
http://www.voyeurmods.com/index.php?action=item&id=1654&prevaction=category&previd=2&prevstart=0
OR
Swiftech Hydrix (conductive) add distilled water $2
http://www.voyeurmods.com/index.php?action=item&id=1591&prevaction=category&previd=2&prevstart=0
Coolsleeves 625 (helps to make sure hose doesn't kink in tight bends $2.60 per length
http://www.sidewindercomputers.com/swco625.html