It seems that for cables, it's important that they are "MFi certified". But what about the USB wall socket adapter? How important is it to get an Apple certified one, or should any third-party one (like those $2 ones on Ebay from China) work fine? Looking at Amazon, I actually don't see any USB wall socket adapters that say they are "MFi certified". The only things I see that say "MFi certified" are cables.