CPU upgrading questions

So I have a Sandy Bridge i7, and I think it's time to upgrade (its bottle-necking my 7970). So I've been doing some research and I see that the newest (haswell) generation of intel processors aren't that big an improvement to justify putting down 300 to 400 for a new CPU and then another 100 for a motherboard.

Should I get an Ivy Bridge? Or should I get a Haswel for the future? I'm still a bit of a noob to this, so don't mind imparting any pearls of wisdom.

what exactly are you doing that a 2700 is bottlenecking a 7970?

really neither an ivy or haswell desktop i7 will be worth their price coming from that