The Micro is the best GBA. But if you want to be able to play older GB/GBC games, you should get the GBA SP Mark II. The first GBA's screen is horrible. But if you don't like the D-Pad on the GBA SP Mark II, you should have a Micro for GBA games and then a Game Boy Color for older GB/GBC games.
Or just use your DS Lite when you want to play on the go, and use your Game Boy Player when you want to play on the TV. I don't see why you need another system if you already have a DS Lite and a Game Boy Player. You can play every Game Boy game except 2 or 3 now.












