You need very expensive air cylinders with very expensive valve control system to achieve fast and precise motion quality.
Hydraulics are the best, but they will run you into the $10.000 range only for the actuator system.
Your best bet is electric DC motor based actuators, since they are very cheap and there are a lot of drivers (h-bridges) available.
At the moment there is no ready to use DIY electronics available to control a hex platform, but you can put together more controllers for more actuators.
The problem comes when you have to control the positions of your 6 actuators in sync with each other, depending on the 6DOF position.
You can run the stewart algorithm (has to be custom tuned for your own geometry) in software, then output the calculated positions to each of your actuators.
For a quick example, here is a closed loop (positioning) DC motor controller: http://www.pololu.com/catalog/product/1393
You could use 6 of these, with 6 DC motor actuators like in your ebay link.
If you have the capabilities, you could consider building custom actuators that accept a variety of DC motors and screw shafts for flexible gearing.
After the actuators and interfacing is done, you will need a math plugin for the Profiler to take care of the geometrical calculations and make sure the actuators are not working against each other.