A pandora you say? Handy to have around if it bricks. I have my PSP open edition-ed and the things it can do now are awesome! Sad thing about the PSP is the lack of good games for it. I mainly use it to play PSX games that I have converted across. Chrono Cross is awesome and I never got to finish it...
The PSP has some fantastic emulators for it. Like the DS, 8 Bits run fine, the SNES is a little slow every now and then, but there is a perfect Megadrive one. I love walking around with a Megadrive, Master System and a playstation in my pocket!!
I didn't even know about the R4 card for the DS. Something to look into though thats fer sure.