Agree with Zetr0 and I'd go for the 1200 myself if I was primarily going for a gaming machine.
An alternative could be:
ACA620 with 16MHz 020 and ~11MB fast RAM
8GB CF card
Kickstart can be loaded from HDD here using ACAtune, but that can also be done with the 500+ using skick (although using fast mem). Pricewise I would think it lies between the other two. Due to the 020 CPU, it should run a few more games than the 500+ setup.