1) DDR3-1600 is in the "decent" range of speeds. The lowest decent one, but still respectable enough. The current consensus is that perhaps 1866 is the price/performance sweet-spot, but 1600 and 2133 also good choices.
2) If you're going to get a GTX 670, I recommend EVGA's FTW Edition
. It uses the PCB and cooling system of the 680, so it'll be a bit higher-quality. Plus EVGA's service goes without saying.
4) The difference between the pro and regular versions of the Samsung 840 is that the Pro uses MLC (2-bits-per-cell) NAND like the 830, whereas the non-Pro uses cheaper TLC (3-bits-per-cell) NAND. The biggest tangible difference will be the write performance of the non-Pro being markedly inferior.
5) Do not get that NZXT PSU
. It's ripple and noise characteristics are outside of ATX specifications
, and NZXT claims that it only guarantees the performance of it up to 35 degrees Celcius. You'd be much better served with a higher-end model like Rosewill's Capstone 750-M