The benefits from Z68 over H67 are the ability to overclock and SSD caching, if you aren't overclocking or do not need SSD caching, getting Z68 over P67 or H67 is unnecessary. If you aren't overclocking, it is unnecessary to invest in a K-edition CPU.
Another thing is that you might want to re-use your old RAM if it's DDR3, or, if possible, get Kingston ValueRAM. They might look ugly because they don't have heatsinks, but are very cheap and low profile.
You'll might want to look into a different case, as this one has, as far as I know, very limited cable management.
Reusing your current mouse and keyboard might be a good idea as well, as the current keyboard and mouse are very expensive and could be bought at any time.