Matching latency/ memory timing

If you get RAM with different timing some mobos can handle it and clock down the faster RAM to run with the slower. However, many mobos cannot. I think that trying to mix RAM with different latency will get you nothing but BSODs. You are better off buying identical RAM to avoid having to RMA your purchase.

really appreciate your advice would you have knowledge about an ASUS motherboard
ASUS P8Z68-V LE Intel Z68 Motherboard and if this MB could handle the difference?

I cannot do anything but guess. I recommend that you stay with the 8-8-8-24, or the 9-9-9-24 (which ever you currently have). The problem is not the speed of the RAM (which mobos can arbitrate) but the latency. If you were mixing DDR 1333 and DDR 1600 with the same latency I would predict that it would work as DDR 1333. But matching the latency is another problem. I have not seen any reports of people mixing latencies and having a successful result.

sound adivice, I was just considering because of a price difference, but I think I will opt to stay will all the same spec's for all the ram..Thanks for your input.

You are very welcome.