Faster memory vs cost...?

Which of the following memory is probably faster??
Mushkin redline CAS 6 ( dont see this often anymore) at 1600?
http://www.newegg.com/Product/Prod [...] 6820226052
or
OCZ reaper at Cas 9 1866 (what an odd number)
http://www.newegg.com/Product/Prod [...] 6820227382

One more question is If i oc the mushkin would the cas remain at 6?

There are a few RAM tests out there that indicate that CAS latency has a much larger effect (relatively) on performance than RAM frequency, at least for multicore processors. Higher frequencies gave better benchmark testing, but with real world apps and situations, it was lower latencies that gave better performance over jumps in frequency. Depending on the degree of overclocking, the Mushkin timings of 6-6-6-18 at 1333 even upped a bit may well still outperform most RAM with higher latencies at 1600.

Since benchmarking performance numbers are from synthetic test suite apps and don't translate well to actual performance with real world apps, I'd go for lower latency over an increase in frequency. Even RAM with higher latencies usually need to have the timing adjusted with more extreme overclocks, so you usually still wind up ahead by going with lower latency memory.

3x2GB, definitely.

Oh, and Fargus, what tests are you talking about? The ones I've seen show the opposite - they show frequency having a larger effect than latency, although the effect from either is quite small. It also seems to be very application dependent, with some apps benefiting more from low latency, and some benefiting from high bandwidth.

Here's a good article actually: http://www.tomshardware.com/review [...] ,2325.html

Oh, and between the OPs 2 choices, the actual latency for 1600 CAS 6 has a latency of 7.5 ns, while 1866 CAS 9 has a latency of 9.6ns.

You've only got 3 channels on an i7. 3 sticks will give each stick a dedicated channel, while 6 sticks will have each pair sharing a channel. Because of this, it's actually faster to only have 3 sticks than it is to have 6 (though the difference is fairly small). Also, only having 3 sticks allows for future upgradability, since you have some empty spots to put in more RAM later.