For sps I would recommend a 6 bulb fixture. If you get really addicted and want to keep the higher light demanding sps then your prepared for it. A 6 bulb fixture also allows for much more combinations and bulb choices. I have a 4 bulb fixture and It would have been nice to have one more just to have a 6500k bulb for my macro but oh well.
As for combos? Probably one of each bulb except for actinic. Maybe 2 actinic bulbs because it just makes things pop.
