I don't think the CG5 GT mount is suitable for a 10 inch Newtonian. I have a Celestron 9.25 inch SCT on it and it's fine for visual but near its limit - I wouldn't want to put on anything heavier, and a 10 in Newtonian is longer as well as heavier.
Argo Navis pricing is at
http://www.wildcard-innovations.com....epurchase.html. You need the encoders as well as the computer.