Personally I would work both machines because they both can be fun for so many different reasons. Your A500 as a project probably deserves a hard drive just for the hell of it. A1200's are relatively cheap and you could also start building on that. Each are fun... More is better.
Just don`t get an A1200 and give up on your rather splendid kit. You obviously enjoy the Amiga so just get an A1200 also...
Couple of links for you from the collection
http://www.commodore-amiga-retro.com/amiga/amiga_scuzz86.htmhttp://www.commodore-amiga-retro.com/amiga/amiga_scuzz382.htmThe first shows the Checkmate and the second shows various cards for the 500. Of interest maybe the Viper 520 CD which came from a machine sold as an A1200 in an A500. Hardly the case but certainly a great find. The 500 is a classic machine and kinda is now for the real enthusiast when it comes to expanding. The 1200 is easy-peasy in comparison, so i would try to up the 500.
I am sure you have checked but if you have the plus I am assuming the battery is OK.
scuzz
http://www.commodore-amiga-retro.com
