Which PSU would be good enough for me?
Where are you buying from?
A high quality 650W will be enough. GTX 690 uses about 270W during heavy gaming, and any good 650W unit will have 2x8 pin connectors.
Since it seems you haven't bought the hardware yet, I would strongly recomend against GTX 690. GTX 670 2GB SLI performs the same and costs much less, while GTX 670 4GB SLI costs the same and performs better on high resolutions. For 670 SLI, you would need 750W since few 650W units have four PCIe connectors by default, and 670 SLI uses about 50W more power than a single 690.
If you're only gaming on 1080p, a single GTX 670 handles everything great.
If you don't do anything heavily multithreaded, you would be better off with LGA1155 and i5-3570K. If you do use heavily multithreaded apps but your needs aren't on a professional level, then you would be better off with LGA1155 and i5-3770K.