I have:
Everdrive N8
Everdrive64 v3
Everdrive GB
Turbo Everdrive
Master Everdrive
Genesis will probably be next. I'm pretty sure I'm going to get the Mega Everdrive which is the more expensive one with save states and the in game menu. After that will be SNES. I still can't decide if I want Super Everdrive or SD2SNES. I'm just not sure that the enhancement chip compatability is worth it to me. I own just about every enhancement game I would ever want to play, so I might get the cheap one. That would leave Game Gear for last. I don't think I'll buy that one unless I ever get my video out board installed. If I can't paly the games on the big screen, I won't get much use out of it. GBA Everdrive will probably by done by then anyway, so it would be next on my list.
Then I have to look into the flash carts for other systems (non Everdrive branded stuff).