Well, I wanna start with an easy one, and powering 2 systems (with with a switch and crap) might be a little over the top. Is it a lot harder to do this than doing an SNES, also, apparently there are 4 layers to this thing, and I already have someone selling me a super slimmed down SNES (someone at BH) so I think il tackle this one, then maybe a RetroDuo or an N64 or gamecube.
Also, if im not mistaken, the retro duo only has about 50% of the SNES/NES titles playable nicely.