Do I need a lot of RAM to run AvalonCab? Will it affect the performance of any emulators?
You should not need too much RAM, although the program can be reasonably thirsty depending on the size of its games database. It should not affect emulator performance as it effectively goes to sleep when running games, and any RAM used should be paged to disk if needed by the emulator. My cabinet is a Celeron 2.0 GHz with 512MB ram and it runs fine.