Thanks for everybody's replies. After reading through I think I may have avoided an impulsive decision.
It seems asi air does support alt az, just not for the az gti. I could use the alt az in synscan and asiair for the camera, but I do like the accuracy of the asi air goto and would prefer only to use one app, again the asi air does this perfectly. @Elp the polar alignment takes me about 10-15 minutes to do, maybe I'm just feeling a bit impatient after learning I could cut this out with the s50! I do like the idea of being able to upgrade, add, swap things around with my current set up. Obviously this is something I wouldn't be able to do this with the s50.
Thanks again for helping me decide.