So is the Canon 400D (which I use) in your $5K budget or not?
Anyway three bits of advice:
I would talk to experienced astro-imagers like Jase and get their advice.
I'd choose between wide field targets (implying a APO refractor) and deep space objects (DSO) (impling aperature and rock solid mount) and select OTA and mount accordingly.
So if you wanted widefield an 100mm APO on a Vixen Sphinx plus Canon 400D might fall into your budget.
Deep space - the mount to hold a decent size SCT will be a killer - it will eat your budget - maybe a EQ6 for a C9.25 (go carbon fibre to minimise temperature variant re-focusing) or a 10" Meade lx200R OTA. But I'd reserve some $ for a computerise, motorised focuser!
Your DOB on a G11 + Gemini might be a real goer, look for second hand gear too! e.g.
http://www.iceinspace.com.au/forum/s...ad.php?t=27313 8" Meade SCT plus wedge for under $2K
Ask for more advice and look for a consensus amongst those that actually image the targets you wish! If it is DSO you wish to image - you need a really good mount and great (rigid) dovetails (Losmandy) for your gear. Autoguiding wil become a consideration too at some point - so factor this in to the eventual carrying capacity of your mount.