After experiencing many crashes and extreme slowness with the Atari800 emulator I was excited to find that there's another Atari 800 emulator for the Amiga which is supposed to be faster although less accurate than Atari800. (similar to A64 vs. Magic64)
See here - Atari Console Emulator review:
Unfortunately, ATR format files don't seem to work with it. So far, the only "cartridge file" that works is ATARIBAS.ROM. The review though lists several games that work with it. Does anybody know where to find Atari games in ROM or disk format (not ATR) or know how to convert ATR for use with the ACE emulator?