For WHDload stuff your A2000 020 is going to have the best compatibility.
Going 060 and RTG isn't really going to do much for you if you are WHDLoading games.
A2000 graphics will be the bottleneck. The bigger the screen gets the slower the UI.
An A2000 with 020 and around 4MB 32bit Memory is the Bees knees for WHDLoad.
