with a bios update you could toss in an ib cpu. it not going to be much faster then the i7 you have now. your haswell cpu upgrade would be a waste of money as the newer cpu only 10 percent faster then your old one. I would replace your power supply with an 850w unit and put in another 670 card and sli them. your rig then should last for a few more years without needing any parts.
It would be cheaper to get a good cooler and over clock then a new motherboard and CPU. Your CPU is still very good over clocked. There really isn't a bottleneck if you want more performance upgrade your gpu