Depends on what you are hoping to house. There are softies like mushrooms and Zoanthids that do not require as much lighting as most other corals, however, they still require a significant source due to their dependance on zooxanthellae, which is photosynthetic. Your best bet would be to buy a strip which housed at least two bulbs where you could go for a good 10,000k + a 6,500k 50/50 w/ actinic.
If you can't, I would say opt for a 15,000k for a single.