Timing does matter a bit. I also try and make sure I get RAM that runs at stock voltage (1.5v in this case) and has decent timings CAS 9 is good for DDR3. With that said, I don't see much difference between 1333 mHz and 1600 mHz, unless your using an AMD Bulldozer CPU or Llano/Trinity APU.
with new ram no. it not the brand of ram now as there only 4 or 5 chip makers there all using the same chips..it the warranty and cs of the vendors now and is the ram your buying on the mb or pc vendors qal list of ram that been tested to work in our mb. gskills customer service is lacking there only few people in the us office in cal. I say this as i bought a 16g ram kit before the z77 mb came out. The ram i bought i found out was not on the ram qal list and would not work. called the ram dept told them the ram was new and fine but was a issue between the ram and mb.I siad i needed another kit and would send them the mb paperwork with the ram qal list with it all i ask gskill was the ram not be red or blue in color. two weeks latter i get the same ram kit back. called the ram dept and they said there was no notes about that you needed another brand...blaw blaw blaw,.i said to the csr how could you not miss 12 sheets of 9 by 12 paper stappled to the the ram with the first sheet said do not send same kit back will not work. crucial on the other hand i and an older p35 mb found out 1066 ram and it did not mix. crusial rma dept did a few cross ships and at the end if needed would have refunded me or replace the ram with newer ram. i would also look on gskill web page they do have a long list of people looking for where the rma are under the forum.