Motor selection for an all-terrain 6 wheeled robot

[hexagon]

Hi
I am building an all-terrain (sand, gravel, slopes, STAIRS of 17 cms height,25 cms tread) robot with a 6-wheeled design emulating Rocker-Bogie suspension. It has to carry a payload of 10kg throughout the arena of about 500m. I need to buy motors which can take this robot over the terrains mentioned. Clearly stair-climbing is the biggest challenge.
Please suggest the specifications of motors which can do this task. Presently I think a motor of torque 25kg-cm will do the trick. There is no much constraint in the speed of the vehicle.
Any suggestions regarding the motors and suitable drivers would be great! Also please suggest some sites from where I can procure very reliable motors along with encoders.
Also please mention the important points to be considered to complete this task.

Regards,

[amando96]

What about drill motors and gearbox assembly? Even cheap ones have 19NM of torque which is slightly over 190Kg-CM.

[hexagon]

Thanks for the reply..
Any other suggestions?
Ragrads,