Hi Ben,
Earlier this year I got my hands on an AZ-EQ6 mount with the 200mm F/4 CF Newt. This set up is great and I would recommend it to anyone getting serious about AP. The good thing about this scope is that it provides easy AP because you just put your DSLR on and fire away. It also has enough length to let you look at all the main planets in enough detail for me to be happy with.
I would highly recommend the AZ-EQ6 if you want to get serious because it has the belt driven motor over the gears like the NEQ6 and 5. Makes the tracking smoother. It really is a good mount because the next step up is the EQ8 and that's just too massive unless you have your own mini van
!
Really it just depends on your budget but you don't want to buy something you might find you grow out of too quickly! Good luck with finding something as i was in the same boat earlier this year!
Nick