Get the 3770K. Yes, it runs hotter but this is only to be expected. Its smaller size means less surface area to expel the heat. It still performs slightly better than 2600k, both at stock and overclocked. To be sure the difference is so slight that you will never notice it, but the 2600k is now obsolete and the 3770k is its replacement, and there is really no reason to get the older chip.
PCIe 3.0 is not a reason to get it though. PCI 2.0 already gives you more bandwidth than you will ever need.
One last thing, if games are your thing, then a better choice would be the i5 3750K. It's not better than the i7 3770K but it's much cheaper and no worse. The i7 is worth it if you do a lot of video editing, modelling or simulation work.