There is no reason to buy the OCZ ModXStream Pro 700W over the 600W, as they have exactly the same cable configuration. The difference in the amount of power available on the 12V rails is not significant either (504W on the 600W vs 552W on the 700W).
Personally I think the Asus Sabertooth P67 is not a particularly good/worthwhile board. Either get a different high end 1155 motherboard or save some money there and put that money into a better graphics card - as this is the most important part in a gaming computer.
You don't really get anything from a high end motherboard as they are designed to support aggressive overclocking which is only possible with unlocked K-series CPUs, which are more expensive and not worth paying more for unless as like I said you should be focusing on the GPU first and foremost.
That processor will not work with that motherboard, you need socket 1156, NOT 1155.
Apart from that these days people should be buying 1155 hardware, as 1156 hardware is EOL.
i3-2100 (or other members of the i3-2000 series) is the 1155 equivalent and shouldn't be significantly more expensive.