Ok I haven't read this but i use the GBA Movie Player 2.
It takes Compact Flash cards and has a built in video and audio and text readers. It also runs GBA software fine (i've only tried PocketNes, Goomba and a calculator). However it is limited to that it can only run roms for those emus which are smaller than 256KB however you can download a pocketnes which gets around this. I think there is now a version3 of this device which comes in two versions, a compact flash and a SD card versions. The new version is designed around the DS and so can run in the full DS screen and run DS software (from my point of view this means it can do mp3s without me having to convert to that .gbs format my device likes) although it will need a *me to run in DS mode. Actually I think the old movie player can run DS software if you have a *me. Maybe I should try this sometime. I can provide links if anyone wants more info