I am running 2 OC'd 670's in SLI as well as an OC'd 8350. I am hitting around 700W TDP along with all my other system specs listed when you hover over my avatar, so im certain you will be able to run all that on a 750W, although a bigger PSU does leave you breathing room for future upgrades. =)
I think you will be ok with the TX 750 considering it is 80-plus bronze rated and made by a decent manufacturer.
Was the 603w the minimum needed or the recommended? Usually, they add 15-20% to allow for some headroom and the rare possibility of the CPU running at 100% which never happens outside of stress testing. Also, did you factor in the 4.4 GHz overclock and increased CPU voltage? Even if you didn't and if the 603w wasn't the recommended, you should still be below 750w. Remember, though, that 80-plus bronze means that your PSU is only guaranteed to provide 82% of its rated power when under 100% load. These figures are also dependent on the temperature of the unit. So if the TX 750 is running at full blast in ideal operating conditions and putting out the bare minimum of its official rating you are only getting 615w or 82% of 750w. Having 2x GPUs pumping heat out right next to the PSU could effect the efficiency even more. These conditions are rare but if you also factor in capacitor aging, in a few years you could be the occasional blue screen when your CPU and GPUs are running at 80-90% load. This is why many recommend PSUs well above the required wattage.
That was needed 603 so it said 700 rec , I also put it to 100% load to be sure, I DoD also put the 4.4 oc on,
I am also running a SLI GTX 670 setup with a i5 3570K OC to 4GHz
6 3tb WD HDD
Creative Sound Blaster Z
5 white LED case fans plus 3 more on my 360mm Rad
and am running a Rosewill Lightning 800w and have not had any problems.