As Brent said, you don't need any fancy stuff on the dedicated astrophotography DSLR. I have 1200D and ED80 and it works really well. I haven't used 500D though so I can't compare it. But if you plan it to use it for daytime photography as well then 500D may be a better option.
Also if you want to save few $ you can use
APT instead of
BYE.
As others said, for visual observing ED80 has too small aperture. Either you get something bigger straight away or get a Dob or Newtonian to compliment the ED80 (which is what I am planing to do).