I wouldn't say we're over clocking them per se, we're just stressing them a bit. These machines don't have a spare square centimeter of space inside them (everything is crammed into a brief cased sized box for portability up/down the ladder wells and hatches). These machines routinely receive 8 or more live video streams (HD) and several high velocity data streams (BFT, IBS, etc) and are also expected to serve up a fused COP feed (track correlation and fusion engine running in the back ground) to multiple consumers. Even then, it's not some much the speed, as it is the lack of airflow (based on the needed dimensions). We literally can not get enough airflow over the second Xeon (it was getting fried from the heat), so we went water cooled. Problem solved. This system couldn't exceed 28" in any dimension (which coincidentally is just small enough to fit through a submarine hatch or other vessel's small hatch. That's a tall order with three fold out HD screens, a crap load of storage and a server grade backplane with processors... To give you an idea of how dense these machines are, they weigh 85lbs each, but fold up into a little cube to meet the dimensional requirements.
Damn! That's a lot of "server grade" components crammed into that enclosure. Impressive!
If you have to ask the price, you don't need it in this case...