I have a telescope at home, however my telescope can't show anything on planets and nebulas except for dots, so I'm wondering if purchasing the 60Da would be worth it or if the 60D would be fine, because I don't want to buy a stronger telescope just to take great astrophotography.
I think a stronger telescope is the better way to go based on what I read here.
From what they say the camera would be aimed primarily at doing 1 thing well & everything else would create extra work in post processing for day to day use.
If you're looking at buying a 60D as your primary camera, rather than buying a second camera for astrophotography, I'd recommend the 60D. There are snap in Ha filters for astrophotography (I can't recall the name at the time but if I find it I'll let you know), that will allow you to use the camera for both astrophotography and regular photography. Either way, if you want to do anything beyond a sky full of stars and the Milky Way, you're going to need a tracking mount of some kind as well.