BTA vs. Koralia

Generally a 6 months to a year is considered mature. You are right about there, and if your tank was cycled thoroughly, you should be fine. It's the small swings in parameters during the day (which we don't see) in a young system that make it unstable.
I'm not really understanding how you are saying you are putting out more light with two bulb 65w CF than a 4 bulb T5 though. A 4 bulb T5 is "only" 96w, but the par value they give out is significantly more than a 130w CF fixture. Par values are more important than the wattage rating. The wattage rating is only indicative of the power it draws to be powered on, not the power it transfers into your tank. Not all watts are equal. The perfect example is taking a 65w CF and comparing it with a 70w MH, you will see what I am talking about. The difference in brightness between the two is staggering.

 

Hmmm. Maybe I should do some research.