yes, lower CAS is better, but as you go from ddr to ddr2 to ddr3 the timings will go up higher.
Latency is the number of clock cycles it takes for the Cas to refresh. More cycles=longer time before grabbing more info. But this only counts when comparing apples to apples (meaning one speed to a stick with the same speed). Many people will overclock their RAM at a higher frequency, but need to loosen the Cas latencies a little higher to do so. This is typically more beneficial than a slower speed with a lower latency.
so if you want to overclock alot a default higher cas is better so you can bump it up a lil to accommodate the higher clock speed but if your a type of peson who dosent like that stuff then the lower one is good
Is there a big difference between 1600 speeds and higher? Ive seen people discuss this subject and they say 1600 is the only really major point where you see a difference, the higher up ones aren't noticeable?
im running 1600MHz (crosiar vengeance 8GB) right now i hit 1860 MHz and i saw a half load difference in windows and steam was instant but i didnt want to risk the life span. i dont know what 2800MHz is like but i would look a videos comparing speed of ram an timmings all in all it really depends if you want to overclock or not.
honest opinion get the overclockabe ones and go to ooooo round 1850MHz
EDIT: one of my friends dad build a system for his one of the guys in his squad they OC the ram to 2800 and he plays BF3
I don't think that dominator ram will interfere with the noctua dh 14 i've had gskill ram in my rig before with pretty high heatsinks, either way I can just swap the heatsink facing upwards since my rig has vents upwards