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I think the best way to approach which scope you should get is to work backwards from the type of images you want to produce.
As Clive mentioned - what focal length do you want to shoot at? What type of images do you prefer?
An all round best compromise focal length seems to be about 1300mm in my opinion. Mike's AP152 with its flattener shoots at that and so does my TEC180.
For example this image was taken with a FLI ML8300 (same chip as the 583) and the TEC180 at 1260mm. This image is cropped but you can see the image scale you will achieve with that focal length. It suits a LOT of objects. Wodaskis CCD calculator (free) is very good at showing what image scale you will get with different scopes and camera combos. Try downloading that and seeing which focal length/F ratio you find pleasing with an 8300 chip.
The next thing I think is important is F ratio and that of course implies aperture.
If you have decided around 1300mm focal length then the lowest F ratio you can get is best or in other words the largest aperture you can get is the best. F10 is pretty rough to image at and the images with a 583 camera will be super zoomed in. The images will require lots and lots of exposure time as you are capturing such a small segment of the sky. F5 to me is an ideal F ratio and if I can't get that then as close to it as I can. I have had several scopes around F5 and they have been very good for imaging.
Next consideration that limits the above is how much weight can my mount handle accurately?
There was a carbon fibre tubed, feathertouch focuser, installed fans for cooling Vixen 260 on Astromart recently for $4000 or less. That seemed a bargain. I think it even came with a reducer. It is light, well made, consistently gets good reviews and your G11 would handle it well.
It is the formula that seems to work for imaging - 2 mirrors and a corrector or an APO and a high quality reducer or flattener.
A 10 inch Newt with a Wynne corrector and around F5 would be one choice.
One approach is to see what equipment people are using that you like the images of. And then narrow that down to what will a G11 handle. I imagine a 10 inch lightweight Newt may be the limit for accurate guiding.
Greg.
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