What Should i Upgrade

If you're planning to upgrade in August, I would say hold onto your money now and use it then.
What are you planning to upgrade too in August? (new platform?)

No i plan to have about 400 dollars by august to spend on upgrades

It would be useful to know what you use your PC for.  

I mainly use my pc for light gaming and video editting along with the occasional 3d modelling and game creation in unity3d

If you upgrade your motherboard to a Z75 or Z77 you can overclock your 3470 using the turbo multiplier. That is an option.

You can also upgrade your graphics to a 7950. They are costing about $300. I would go for the gigabyte model since I like its cooler.

Your CPU is plenty strong right now. If you did want to upgrade that, I would go for a E3 1230v2 and overlcock that with the turbo mulitplier. Better than getting a 3770.

I would suggest grabbing the motherboard or CPU now. Haswell will not be a major game changer so no sense in waiting for that. Then after the next gen of GPU's hit, maybe grab one of those or a 7970/680 when they drop in price.
Selling off your 3470 and old board and gpu will offset a lot of the cost allow you to buy a better PSU as well.
Unfortunately, your main limiting factor is the 7770 right now. You could grab a 7870/7950 and grab another to crossfire with when prices drop.