This is a tough question to address without more information.  How much are you willing/able to spend?  How fast are you currently?  Are your planned Oly/HIM races hilly or reletively flat?

I'm a cheapskate, so I really like my FlashPoint FP60s as an all around race whell that didn't break the bank too much.  Add a wheel cover for $80 to convert the back wheel to a pseudo-disc when course conditions warrant and it's a fairly affordable alternative to consider.

How about 606;s all around. then go to wheelbuilder.com and just buy a wheel cover for $80 to turn your rear into a disc when you want that extra speed. I posted the same in one other section, IMFL 2008 Winner Tom Evans used one, no one had a clue. then when you don't want to use your disc, just remove the cover. Its safe, secure and you still get that cool  woomp woomp woomp disc sound like the pros do...

I have 404's with one. super easy & budget friendly.

Have you considered just renting race day wheels?  Some real advantages there... always on the latest technology, you can pick your wheel set to better match the expected conditions, and often more affordable unless you are riding a lot of races each year.