I'd have to think Crucial is being conservative. Take a look at the Ballistix PC4000: the thing runs 2.5-2-2-5 up to 241 at 2.8 volts. And what is it rated at?
Hopefully they aren't doing a switcheroo thing, you know, early sticks with best binned stuff for the reviewers, then complacency after that.
Your best bet of getting the 2-2-2-5 sticks is Newegg. As they are more expensive than Crucial, they might still have the 2-2-2-5 sticks in stock. No guarantees though, as they move stock fast.
And a tip here: GET 1 GB RAM!!! My preliminary testing of the 6800 Ultra and X800XT PE with Far Cry and Doom3 is you get bad stutters and freezes with less than 1 GB. You're talking monster cards, so it's not the card. I wish I could try 2 GB. While I have enough sticks, doubtful I can get the same overclocks with 4 sticks, plus you will lose PAT.
And for best performance, you need max bandwidth at fast CAS settings: 2-2-2-5 or 2.5-2-2-5. Even 2-3-3-6 ain't gonna cut it at 1600x1200 with all the eye-candy. Slow CAS = mouse lag, shuddery pans, you know, the nausea.