The problem with DS is that GBA games look really small, and the original GBA is a pain in the ass because the lack of light. So SP is the best system to play GBA games. (Or a GBA emulator on a PSP like I do this days)

For playing GBA games? GBA SP the later model with a backlight. The older model of the SP has a frontlight that turns on and off, it's not terrible but you don't want that one. You want the one with the adjustable backlight, it has much nicer colors and is easier on the eyes and is brighter.

Make the psp a Pspgo and add the abilty to play on the TV and use a PS3 controller for the GBA games.

DS lite.

You should play Fusion, Zero Mission, Minish Cap and Mario & Luigi: Superstar saga.

Why would anyone want to play GBA games on a big tv?

Even Ninty thought it would be a great idea.

Ninty also thought the Virtual Boy was a good idea.

Would definitely say don't knock GBA on a proper screen til you've tried it, some games look and sound lovely, Minish cap is beautiful even at 42"

I have Minish Cap, Zero Mission, Fusion and Mario & Luigi: SS on the Wii U VC. Gamepad is the way to go.