If you are going to OC memory, something that I don't recommend as the performance gained often simply isn't worth it in terms of increases versus headaches with stability, then manual configuring is the way to go. I recommend you go with the cheaper of the 2 and drive on. Good luck!
The CMX6GX3M3A1600C9 is the newer version of the older TR3X6G1600C9.
XMP is a dual edge sword and in most instances is limited to the first set of RAM, and the CAS will be set correctly. The other side is if the BIOS doesn't recognize the XMP correctly you get post failure or a host of other oddball problems. You'll still need to manually set the Speed and should set the DRAM Voltage if you're OC'ing the CPU.
In most instances since I need to set most everything, I disable XMP and manually set the RAM.
XMP is more of a marketing gimmick than an actual capability (my opinion only). You can squeeze more from manual settings than XMP will do on its own. I personally would use another brand altogether, such as G-Skill or Adata. You get good performance for less cost.
"Better clockers" is subjective to a bunch of factors. I am using G-Skill, Adata, and Corsair memory. Of the 3 brands, I am happiest with the G-Skill and I have been able to get the most from them when I tinkered with the settings.
However, once I tinker, I always return my memory to stock settings. OCing memory just doesn't produce the same sorts of performance increases you see with CPU and GPU OCing. And, you can make your overall system flaky with the least little config issue with OCed memory.
Here is my best advice, all of these brands are okay. Get the best bang for your buck (pound) and be sure you buy a product with a lifetime warranty. All discussed will meet your needs. Save some geld and have fun in the process!
Tell me about it, many hours of changing every setting on DDR then benching, then running hours of testing, for what.? Thats right..14 more points on 3DMark and a .22GB/s increase on Sandra.
I guess my best performance option is to buy the memory with the tighter stock timings if thats what I'm after.
They do the 7-8-7-20 timings set for £100. http://www.scan.co.uk/products/6gb-(3x2gb)-corsair-xms3-classic-ddr3-pc3-12800-(1600)-non-ecc-unbuffered-cas-7-8-7-20-xmp-165v
I'm still messing around with DDR2 and have found that the performance increase after hours of tinkering is noticable but makes me ask if it was worth all the time and headscratching.
Hopefully a 950 @4ghz+ and 6 gig of ram will give me the boost I'm looking for without the headache.