First Welcome Aboard!

Tthough the actinics serve to benefits our captive critters, the color ranges are geared towards pleasing our eyes, the 460nm will appear more blue, the 420nm will be more towards the indigo/purple end. Those wavelengths alter the way the the flourescing pigments appear, reflecting back the vibrant colors. The differences can be pretty dramatic between them. Particularly with power compacts the actinics are benificial to reach the shorter wavelengths where 1/2 of the photosyntesis takes place, flourescent daylights tend to be more towards the reds. So the combination works out nicely.

As for daylights, 10000K vs 6500K, the 6500K will have a more of a yelllowish hue to them than the 10K's, but not all bulbs are created equal for any color range. Though power compacts tend to shift spectrum pretty rapidly with age.

Most manufactures publish a graph depicting the average output of each bulb type to give you a better idea of the spectrums the bulbs should perform best at.

The combo bulbs I think you mentioned the 96w quad PC's do a nice job with the 50/50 particularly with shallower tanks, they should give you nice crisp lighting, combined with a good reflector they will be able to reach even deeper into the tank.

Hope this is of some help.