Shawn, I believe you should be able to achieve similar results with your 40g. Adding another 2 bulbs, if possible, is an excellent idea, especially given your plans to keep sps. IMO, the T5 actinics don't do much for sps. If you've got 6 bulbs to play around with, try 4x AB Special and 2x Blue Plus. You could potentially replace one of the ABs with a 6500k but personally, I prefer the AB for its intensity and more complete spectrum.
rj, thanks again. I think you will see better results by replacing the actinic with a Blue Plus. I'm currently running 8 T5 bulbs. If I had 9 or more bulbs, I would consider adding an actinic or two for visual effect, mainly when the other lights are off.
Dan