Well, if you already have two GBA's, then I don't know if you will want to shell out the $200 bucks for 2 new SP's. But, I will say, not only is it being so small incredibly nice, I couldnt imagine not playing without the new backlight on the GBA SP.
They are defentitly worth the money, however if you already have two Im not so sure. If you got $200 bucks laying around, go for it and sell the old two.
Oh, and also, you can already get those adapters for gamecube, I'm pretty sure they have them at
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