I'd just build or get a cheap computer, a modern TV has VGA inputs anyway and you'll get waaay better emulators.. Although, the psp idea is tempting.
Oh, yeah, and I did emulators on wii using the zelda twilight princess save exploit, if you really like those ridiculous hassles.
, I have a job now *sigh*
"WHAT!? I don't even have a computer, I post this with my Wii!"
I have done it with both the Dream Cast and the Xbox. The Dream Cast is only good for NES games and requires that you burn a special Rom disk but no modding of the console is required. The Xbox had far superior results as you could play roms for just about any console up to the Xbox. I focused mainly on the SNES, NES, GBA, MAME, and Sega Gen. All worked great. You can soft mod the Xbox without any hard ware mods required. I believe I posted some links on the forums here to help someone else.