Slightly flawed in your reasoning. The RAM speeds come in handy when you overclock. Below is a link to a thread that I learned all about this. When you overclock by raising the FSB, the RAM usually gets overclocked at the same time, automatically. Because the Conroes are Intel chips, they are quad-pumped, meaning the FSB is only 1/4 of what they advertise. In other words, the 1066Mhz FSB Conroe chips have an FSB of 266Mhz. (266Mhz * 4 = 1066Mhz)
The RAM is DDR, meaning Double-Data-Rate. Essentially, DDR-667 only runs at 333Mhz. (333Mhz * 2 = 667Mhz) Your RAM speed must match your CPU FSB for performance, it will hurt you if it is slower. That means that DDR-667 (333Mhz clock) is about right as far as speed goes for a 1066Mhz FSB (266Mhz) Conroe chip. If anything, DDR-667 is a little overkill.
So congrats, if you can afford it, go buy $650 memory, just because you can. But remember that your DDR-1111 is going to run at a clock of 556Mhz. Your processor FSB is going to 266Mhz. (Even the Extreme Conroes are 1066Mhz FSB.) It is always a good idea to have the RAM running a little faster than the CPU, because some applications can take advantage of it, while others cannot. With a 266Mhz CPU, I speculate that anything over 350Mhz (for your RAM speed,) would be in the realm of overkill. With your 556Mhz RAM, you will have approximately 206Mhz of RAM speed as overkill. That's approximately a third of your RAM speed close to unused, meaning approximately $216.50USD going to waste. Justify that it's worth it.
Now, you ask why people would make RAM that fast if people don't make processors with FSBs as high as 556Mhz? Simple answer, overclocking. Some of the highest FSBs I have ever heard of aren't over the low-600Mhz range. When you overclock, raising your FSB raises your RAM, respectively. This means that when you start to raise your Conroe's FSB, the RAM increases with it. (Duh.)
We both know that it's a good idea to keep the RAM and FSB not too far apart, because they like to be close with the RAM a little higher than the FSB. (As I just stated above.) Theoretically, you could start your 266Mhz Conroe in it's climb, and begin raising the FSB/RAM. If you think about it, it almost makes more sense to buy high-quality low-speed RAM that slightly exceeds your CPU FSB speed. For a 266Mhz Conroe, I'm thinking somewhere around DDR-667 (333Mhz) or DDR-800 (400Mhz.) I read that this board likes DDR-800.
When you are buying lower speed of RAM, buy the highest quality you can find. People often buy higher speeds of RAM because the chips used in them are of higher quality. Don't confuse "RAM speed" that I keep referring to, with "RAM latency." (CAS3,4,5 or whatever.)
Heres a link to a post that would probably clear up a lot that I didn't here.
Link
Wusy (Are you senor 29k posts?) if you see something wrong with this, or anybody else for that matter, please tell me.)
In my opinion, you will always get better performance out of high-end equipment that is set up exactly right than top-of-the-line equipment that isn't set up correctly.