the head on the Slik sprint pro can indeed be removed..
it was actually funny, i was at the camera store (penn camera here in d.c.) and picked up the Slik..
playing around with it, i was amazed at the weight, and i was totally convinced that the tripod was carbon fiber because it was one of the lightest weighted tripods in the store (it is aluminum construction),
i asked the guy if the head was removable as i was twisting the head..
the store clirk looked at me and scoffed "no the head is not removable, you need to get one of these if you want a remove..." he trailed off and staired at me dumbfounded as i unscrewed the head and removed it in front of him..
"ohh. i had no idea you could take the head off" he exclaimed with true astonishment..
now the screw is a 1/4 20 standard thread so regular higher end heads with the 3/8 16 scrw won't work unless you have an adapter, but Slik makes differend heads for their tripods and other third party heads with the same screw mount should work fine..
here is a list of heads by Slik
I have the 5Dmk2 and the ball head that came with it does fine holding my camera with the canon 70-200MM f2.8 attached..
just remember to hold onto the camera when loosening the ball head because it lets go quickly and the camera can flop down..