Hi John,
XPS 8300 has a motherboard with the Intel H57 Chipset which will not support 4 GHz processors. However, a motherboard with Intel X79 Chipset with Unlocked BIOS for Overclocking will be compatible with the following Intel Processors:
-- 2nd Generation Intel Core i7-3820 - 10M Cache, Overclock up to 4.2 GHz.
-- 2nd Generation Intel Core i7-3930K - 12M Cache, Overclock up to 4.1GHz.
-- 2nd Generation Intel Core i7-3960X - 15M Cache, Overclock up to 4.2 GHz.
These processors are currently shipped with Alienware Aurora. You can choose any one of them.
