In my opinion, there are three things that will limit your ability to overclock this processor.
1. The BIOS on your mobo. I recently built a sys and the BIOS had no method of changing voltages or frequencies, so i had no method to increase the clock speed of the CPU.
2.Temperature - If you are able to increase the speed of your processor you want to watch your temps. Some would say that 60 degrees C is absolute max with 50 degrees being the average maximum operating temp. (i hope that makes sense)
3.Recently AMD has been "locking" the clock speeds on their CPUs. There are methods to "unlock" but you will have to do a little research.
Lian Li Aluminum Case
Intel D975XBXK2R Mobo
Core 2 Duo E6700 CPU
EVGA 8800 GTS Video Card
Corsair XMS 2 x 1gig RAM
Zalman 9500 CPU cooler