So the upgrade from i5 to i7 is $135, 4GB to 8GB is $90, and 128GB to 512GB is $720. I'm assuming the processor and memory upgrades are definitely worth the extra money; but is even the $270 jump to 256GB worth it? The 11" MBA isn't going to be my main machine, so at most I would be storing apps, a few games, and some media. What's the recommended "sweet spot" betwwen price and future-proof? Thanks.