[VS6000 (Tim)]

So I recently bought a star adventurer which I'm very happy with! Using a d810 and 70-200 2.8 and getting 2 minute subs reasonably easy so that's great.
What I'm now thinking is instead of getting a 2x converter for this lens to get a less sharp 400 5.6, get a proper telescope.. I take that it's a good idea for getting better images? I love the horsehead so something in that focal range I guess. Budget I guess would be under 2k, the less the better depending on bang/buck.
Also guessing with a scope comes the need for guiding too? That's totally foreign to me but I'll learn if need be!
Any suggestions?
Cheers! Tim