Best system for Portable Emulation gaming

I was wondering what is the best system for portable emulation?

I want play NES, SNES, Genesis, SMS, Turbo Grafx16/PC engine, MAME, CPS (most variations), and PSX would be a nice addition, but not needed.
If possible I would like to listen to MP3s and watch some movies would be good as well.
A nice screen would also be nice.
I know with all of that said, is the PSP or PSP go the best option?

I was looking at the DS, DS XL, PSP, GP2x, Wiz, and Canoo.

As far as I know the PsP would be your best bet. I don't know if there any MAME emulators for it, but I definitely know off the top that it has NES, SNES, Genesis, and N64 emulators. Or, you could save up a little more and try to go for a Laptop, because that would cover all that you want, haha.

I have a laptop/computer for emulation at home, but I wanted something portable for gaming on the go. So would PSP or PSP go be better?

I would try the PsP go.

Is the PSP Go hackable? I dont really care for PSP games, mainly just the emulators. I would assume that you need to change the firmware to get emulators to work, right? Especially PS1 games?