First, I have missed it so what is your tank size? Second, what type of plants do you want to grow? These will decide if need to get another bulb or stay with the one you have.
Actinics will absolutely help plant growth, no doubt about it. The wavelengths that actinincs ahve is very beneficial to plants.
That being said, you still do not count actinincs toward your total wattage nor lumens. They are not bright enough to affect the numbers enough to be beneficial.
Example. 55 gallon tank with a quad bank of 96 watt power compact flourescents. Going with 4 high light bulbs would give 384 watts and almsot 7 watts per gallon, way too much. If you put 2 full spectrum bulbs and 2 actinics you have 196 watts of countable light and 2 that have the spectrum needed but don't make make it a blinding light.
The best setup is to have multiple bulbs of which you get the needed wattage and lumens as well as other bulbs that finish out the spectrum for the plants to thrive the best.
Find what wattage you want, then put actinics in there to take up the other spaces. When I finally get the tnak I want I will have enough slots for 20 watts/gallon but will have less than 4 w/g because of the multiple "wattage uncounted" bulbs I will have in the fixture.