A couple of thoughts. I run Helios 20Ks on my tank. I have actinics (VHO), but I don't run them when the MH are on - they color THAT nicely! There are a bunch of other folks here that also do the same.

We got them from marinemadness.com, in a group buy for $39 each. I seriously doubt you will get near that price, but I believe they are available in an HQI (DE) bulb.

An RO/DI unit with a top off is what you will need...