I agree with everyone else, go with a small APO refractor for now. They do just fine for visual, and excel in Astrophotography. I have a RC8 and very surprisingly, it does quite well in visual, considering it wasn't designed for it. I find my 17mm Stratus to be a perfect combo for viewing. You definitely need a diagonal otherwise you will break your neck, same applies for if you get a refractor. You don't really need anything else for the RC8, it's fine as is. Also I have a NEQ6, and I can tell you that a HEQ5 would not be able to handle it, especially once you start adding cameras and guiding to it. The mount is by far the most important item in your arsenal, and I know you mentioned you cant afford it but if you can save up a little longer, I'd say get a NEQ6. Even if you dont plan to image with 10" beasts. It was a diabolical cominbination with my 80ED, I could practically kick the damn thing and the stars wouldn't move (Though advisable not to repeat my experiment lol).
I personally went through quite a few scopes before settling on a RC8. With a CCDT67 (Focal reducer), it becomes a ~1000mm F/5.6 scope so it's kinda like a two in one. But it is quite challenging to guide at these FLs compared to a 80ED or the likes, and it might be so hard with a RC8 that it will put you off Astrophotography for a very long time trust me. Be sure to consider other small-ish APOs not just the 80ED if you wish to go down this path. They seem to sell a little overpriced here, I mean I sold mine for $480 shipped to NSW... so keep an eye out for any second hand bargins
an ST80+QHY5 will comfortably guide anything up to 1000mm, provided you have good Polar alignment. And that will take time to perfect!
Lastly an DSLR, even a very old one, will teach you ALOT about astrophotography. My ~7 year old DSLR gave me some of the best pics I've ever taken and dont have to faff about with cooling, drivers etc. Just turn it on and click. So just take your time and see where it takes you
Good to see you're atleast doing your research before delving into it. Good luck!