pfft

High-end cases ftw! AIOs ftl.

Tower based cases have always been so much more useful and functional.

Either way, getting back on topic, I would vote for the 580 over the 575.

OP, it is up to you what one you want to play with first, but, since you will eventually use em both I would not say that it such just a big deal and you can choose what you like more based on your experiences with them.