Sounds like a decent deal.
420nm is actinic and not very useful in planted freshwater. Mostly used in marine tanks and people sometimes use them in African Cichlid tanks to pop colors.
For plant growth stay between 3000K and 10000K. The lower end being very yellow and the higher end being very white. 6500K is about high noon looking. I prefer 8000K myself. The important thing is that the bulb says "full spectrum" somewhere on the package. You will be told to only go with 6500K or 6700K bulbs by many people. Unless you are looking to get into optimal growth rates, CO2 and a strict fert regimen then just stay with a color temp (K rating) that you prefer.
Since you are considering going T5HO keep an eye out for algae and nip it in the bud early before it gets out of hand.