There's a few options, but what is best for you depends on what spec machine you have. For a lower spec machine (040+aga or lower) MagiC64 is probably your best option. It's not as compatible as some of the other emulators, but it is fairly fast compared to the others. For a higher spec machine (ppc/060(maybe, not sure how fast it is on 68k)Vice is up to date on amiga os/clones, and in my opinon is porbably the best c64 emulator around, so you cant go far from there. Frodo also has an amiga port for both 68k and ppc.
As for c64 BASICs I played around with Simons basic a bunch of years ago. I was similar to the default c64 BASIC, but faster and had more graphics and sound commands if I recall, plus I think came with a compiler (either came with, or one was available).
