I can second Steves LED's as being a good place to look. If you want Phillips Luxeons he is definately the guy to go to. I used mostly his parts in a 28 LED build for my 37 column and it turned out pretty nice.
On a side note if you want CREE LEDs I would reccomend RapidLED they were also quite prompt and fast.
If I can remember correctly Luxeon bulbs had better color rendering and wider spectrum while CREE bulbs have slightly higher intensity. Of course this is always a moving target which varies from batch to batch and improves gradually with manufacturing process improvement.