I have a Mach II GT unit that I have not used in about 2 years now. I don't know if it still has a Freon charge.
It would easily keep the X6800 chilled to between -62C and -50C on full load.
Besides the added noise, which really wasn't too bad, the cooling solution is meant to install and leave it. Removing and installing the cooling head on a regular basis will cause damage to the flexible stainless steel hose. The other issue is finding a good case to partner it with. The standard case the cooler came with was made from steel with razor sharp edges; however, Lian Li does made some nice cases specifically designed and cut for the Mach II GT. Another issue is for new socket designs needed a new mounting bracket for the head. I would recommend getting a unit that mounts to the motherboard with a universal bracket/arrangement.
Right now I am working on designing and building a cooling system that will revolutionize the computer industry for both civilian and military applications. Funding is the big issue as this stuff is not cheap to play with.
Here are the results of the Mach II GT cooling my X6800 on an ABIT AW9D-Max.
http://premium1.uploadit.org/skiman/ben ... s_ride.jpg