...but in answer to your question, a z77 board will do the trick.
One of those plus an i5 2500k or i5 3750k is possible within your budget. Together with your 7950, you will have an excellent gaming rig.
Nevertheless, the other posters are right. 7950 cannot even max out pcie 2 bandwidth, so you will get no performance benefit over a z68. Therefore, a z68 is a perfectly good alternative.