Yus, the "old" Sandy Bridge stuff is 2xxx series (i5 2500k, i7 2600k and the like) while new Ivy parts use 3xxx.
Personally I just can't recommend i7 for gaming. It does better than i5 in heavily threaded stuff (video editing comes to mind), but has little to no benefit for games. Considering the 30-40% price premium, it's hard to recommend unless someone actually needs it.
Z77 sports some extra features like SSD caching (SmartResponse) and native USB3. Older Z68 matches it for the most part, but the "lower" chipsets miss some features such as being able to use the integrated graphics on the CPU (and
QuickSync, which may or may not be something you want). The graphics part is terrible (for gaming), but at least it's something to fall back on if your card dies. You paid for that part for the CPU anyway, so why not have the ability to use it.