If I had a budget of $8000, and a wish list the same as yours here's how I would spend it.
Meade 12 inch Lightbridge (or similar) truss dob. $1200 Alternatively if portability isn't an issue you could opt for the 12 inch solid tube dob and save around $400.
Losmandy G11S $3499
Argonavis & encoders to suit G11 & dob. $1400
Orion Starshoot Autoguider package. $599
Canon EOS 550 DSLR (Grey import body Only from DWI for example) $720
Canon 70-200 F4L lens grey import $658
That all ads up to $8068, given that you would probably spend over $6000 with one supplier, you could reasonably expect that they would throw in at least couple of extra suitable quality eyepieces (e.g. Orion Stratus)
What you would get for your money.
Dob. The optics and portability of the 12 inch truss dob would be ideal for your needs. Optically, 12 inches seems to be a sweet spot in terms of mirror quality.
The Argo-Navis will give push to capability to the dob, as well as push to for the G11 for imaging. Using the same pointing device on both would minimise the learning curve and any confusion swapping between platforms.
The EOS550D would be adequate for imaging combined with the 70-200 lens as well as providing you with an excellent terrestrial camera, you could alternatively go for an ED80/Field Flattener combo but the initial cost would be higher and the flexibility less. If you already own a Canon DSLR I'd be tempted to opt for the 400mm F5.6 Lens over an ED80/Flattener setup, the 400mm f5.6 would be as fast, close to the same focal length and better corrected (
see this thread).
I haven't mentioned the GPS requirement, it's simply not that important, a rough location of Lat/Long to the nearest 100km or so is all that's needed and you can get an accurate lat/long from google earth.
You would also need some dew straps, controller and a couple of plugpacks.