Don't buy a 580 EXII. Buy a 430 EX II. Do you know what the difference is between these two speedlights?
I don't own either. I have 4 Quantarray 9550s with Canon digital modules. I carry one with me and my wife has one in her kit. We have two as backups. They are less than 100 each. Do they perform as well as the Canon speedlights? No, but they perform good enough to photograph anything I'm taking pictures of. No one has ever said to me, "Wow, your photo would have looked so much better if you had used a 580 EX II. " No one can tell, and no one asks. Light is light, and it all boils down to what you need. Unfortunately Ritz Camera has discontinued the Quantarray speedlights. The good news is Promaster still carries the same model, just rebranded. I highly recommend ...
5750DX
1) twin flash stobe. You can bounce the ceiling and still have an on-axis fill. Two lights in one. Great for perfect friends and family photos.
2) Modular. The flash is two piece. Body and dedicated module. If you break the plastic ears off the module (which of-course is better than ripping the hot shoe off your camera body - that's why it's good not to buy stobes with metal ears) you can replace the module for around 50 bucks rather than replacing the whole flash or paying for reconstructive surgery on the body and flash.
With the 700.00 left, buy a second hand Tamron 17-50 f2.8 and a used EF 100 f2.8 Macro
For 850.00 you'll have a really nice flash with two very capable lenses.