Thinking about going GBA

Hey, I'm thinking about buying another flash cart (giving my old one to my brother) but am thinking about just going GBA with the new one. I mean, I no longer care to back-up my games for I play mostly at home so there's no risk of losing cartridges and, secondly, as much as I will miss some awesome touch screen homebrew (and ImageViewer comic book reading), I don't really want to spend a lot for the few perks. But before I decide I want to know a few things:

1. What's the best flash cart for a DS Lite (sticks out as little as possible, most compatibility, plays back MP3's the best)?

2. How much does it cost? Is it cheaper than a DS one (I assume it is)?

3. Do I need any kind of pass card or do I just select it as I would a GBA game (I'm a newbie)?

4. How are the emulators on it? Regarding SNES, Gameboy, GB Color, and SEGA consoles, what's their status (graphical glitches, sound, etc.)?

5. And, well, I know I said I don't care for back-ups but I do enjoy playing the fan-translated (partially on the one I have) ROM of the Silent Hill Play Novel for GBA. So, back-up playability is a plus.

Thanks you.