Yes to the last question. Also, where are you buying the CPU from?
Honestly, whether or not it's worth it is more of a personal choice.
Most people here will tell you flat out to get the 3570K because it's newer, if nothing else, but it really doesn't matter. Both will last you the same amount of time.
And the 2500K is compatible with 1600 RAM, anyway. It's not "officially" supported, but that doesn't really mean anything. I'm running 1600 RAM as I type and almost everyone I've seen here with a 2500K has 1600 (or higher, even) RAM.
Thanks for the quick, straight to the point answer. That's exactly what I was looking for.