Hi Mark
If you are planning to do astrophotography, I would invest as much as I could into the mount. Even if you are not planning to have an OTA of more than 20kg, something like a PMX is not over kill. They are very good, I have not had any trouble with mine, It is very easy to use and the engineering is suburb, also a pleasure to look at.

The support from Software Bisque is excellent. Yes it is quite an expensive mount, but you do not need to modify it. It works great straight out of the box.
I was looking at the Titan but the unfinished Gemini 2 software put me off.
I don't know much about AP mounts but from what others have said they are extremely good.
Like with any equipment its the $$$ that make any decision hard. But there is nothing worse than spending a whole bunch and then being disappointed.
Do your research, ask as many questions as possible and try to see some of these mounts working in the flesh.
Cheers
Phil