Simple answer is that you cant. Tube lighting is not like a conventional lightbulb. Each starter is rated for a certain wattage and you have to stick with that bulb. The only way to upgrde is to replace the starter unit tp a hightt light output. I.E. get a T5 ballast if you have t8 lighting.
That is what I figured the answer was going to be. Thanks for your help!Now, I guess the question is where do you find T5 ballast with a decent price tag!?