Just a few points, wont come close to answering all your questions but may help.
- The 9.25 inch HD is good scope and you have option of trying Hyperstar work at about F2 I wouldn't go 8". A bit small, C11 even better
- You'll also need to consider a starizona Microfoucser.
- Powermate 5X gives you a hell of of focal length and you miight like to consider the 2" 4x as an alternative. You can use it with 2 inch eyepieces as well.
- You can use the starizona cooling system to significantly reduce cool down time.
- Mount is going to be a balancing act. Long focal lengths require grunt and there a few alternatives.
a) dont know about CGEM's and don't know about the tracking of ISS
b) dont know about the build quality.
c) I owned and didn't like the EQ6 and I believe the EQ8 is problematic for some. Build quality may be an issue but I can't comment from experience. There are threads on IIS that talk about it.
d) I own a G11 G2. The build quality is beautiful but the operating system is a bit of a work in progress. They have been a workhorse for many people for many years for very good reasons, including flexibility and upgradability. Good news is they are pretty cheap at the moment and I think there are a couple in the classifieds. Bad news is they take some learning and you have to be prepared to do the learning. There are a lot of support resources available as well. I temporarily sold mine, then bought it back, which I guess says something. (Let the abuse begin
)
The G11 is incredibly stable as well and will carry a lot of mass. It also separates in to a couple of easily managed units. The field tripod is a good option if you can get it.
- Undoubtedly, some will suggest an Astrophysics or TAK mount. I dont know much about either. Astrophysics makes good gear.
- C9.25 and G11 G2 are well within your budget and there are plenty of Losmandy plates for mounting everything
Overall, you are planning a good scope with a lot of potential to be a workhorse.
Man, you'll sure notice the difference over a 100 mm scope; wish I could be there when you see Saturn for the first time
Rom