Very few games utilize the hyperthreading on the 4770 and almost any game out there needs an i5 to run at its best. I would find it rather wise to invest in a newer GPU for games which would make a world of a difference depending if you're still using your iGPU. Although I guess I could see future proofing apart of your reasoning. Anyways if you wish to OC purchase the 4960K as it has an improved thermal interface making it much better for OC'ing.
For a cooler it's all on your budget. The go-to choice is usually the Hyper 212 EVO in the budget range and the higher end range is split between mainly the NH-D14 (which looks ugly in my opinion but it is still an effective cooler although antiquated; there have been no updates for it since sandy bridge) and the PH-TC14PE (which looks much better and performs slightly better as well). Both high end air coolers need lots of space though.
Regarding AIO liquid coolers, its up in the air really. Mostly depends on the size of radiator you can fit in. I'd say a corsair H80i (or H75 since both offer similar performance but have different styled pumps but the same dimensions) would be the best for your case in terms of fitting the biggest AIO cooler you can in it.
Concerning custom loops, not quite sure your case would support one. Other neat coolers to check out are the ones from Cryorig. They're a recently formed company comprised of skilled individuals from Thermalight. They made quite the impression at Computex and have some great coolers. I'm considering purchasing their C1 (which is a low profile cooler) for my HTPC I'm planning. Definitely a group who knows what they're doing.
Oh and don't forget your thermal paste. Right now most sites (including here at tom's) recommend the Gelid GC Extreme.