and a 2-2-2-5 module will give you about 2% better performance to a 3-3-3-8 module
I don't know about that. If you look at how fast you get with the cas and ras at 2 and the ras precharge at 2 and change them to 3 you'll see a pretty big difference in MB/sec transfer to the RAM. But the whole point of super low latency high performance RAM like the OCZ Platinum series Rev2. sticks are made of high quality chips so they can be OC'd up to 280+MHz so theres DDR550 right there. And since it starts off with a lower latency you can get that nice high MHz and still retain good tight timings.
The Corsair PC4000 sticks I'm seeing are $275 for 3-4-4-8 timings at 2.75 voltage which you could get not only a faster MHz than that with those OCZ I mentioned but with tighter timings and probably the same voltage possibly 2.8 instead of their rated 2.75, but overall the price regarding ultra low PC4000 is comparable to that of ultra low latency high quality and performance PC3200.
So really the PC4000 I don't think is that great for overclocking purposes.