If you read up on the equipment history of all the dedicated astrophotographers here, it's usually just repeated cycles of buy-upgrade-sell as you realise why the entry level equipment that at first looked appealing wasn't suitable.
If I were starting again - I'd probably go for an HEQ5 or NEQ6 (with goto), ED80, field flattener, modded DSLR or OSC cooled CCD, a finder/mini guide scope with camera, dew heaters, upgraded/motorised focuser, a light box, software to streamline things (e.g. BackyardEOS or APT, something like CCDInspector, plus processing software like PI), powered USB hub, laptop for data capturing (possibly processing), and a deep cycle battery + quality charger.
If you're patient, you'll easily to be able to get all of the above within your $1700 budget by purchasing second hand. The benefit is that when you feel the need to upgrade, you won't lose much $$$ as they're all easily sellable items. (Buying new will be well over your budget.)
You'll notice that the OTA actually makes up for a tiny part of the budget - it's not quite as important as other things (especially mount). The problem with getting a big OTA for deep space imaging is that everything else becomes correspondingly more expensive - you'll need a bigger mount, better focuser, better field flattener, bigger sensor, etc etc.
There's soooo much knowledge, skill, and experience that you need to get that set up to work well that it'll keep you busy for ages
I think people - myself included - tend to underestimate the skill needed, and overestimate the need/benefit of giant OTAs - because it's a much less visible part of imaging.
If you read around the forum, you'll see that getting round stars across the entire frame is a tricky business - even for the guys with top notch equipment.
Good luck!