I hear that Petco will have their $ per gallon sale soon. Makes that 40B look mighty tempting.
I'll give you a link to get you to an understanding of the light game, two in fact.
http://www.plantedtank.net/forums/showthread.php?t=184368
http://www.plantedtank.net/forums/showthread.php?t=107303
Some of the LED fixtures are more expensive up front. But most of those are too powerful for a 40B anyway once you find that any light fixture won't give you coverage from front to back of any tank 18" or more deep(front o back) which brings you to
thinking of buying two which are not so powerful that they double each other in light.
I have small(10" front to back)tanks and I don't appreciate it that I get two bulbs that
are next to each other in the T5 fixtures available under $100. So one of mytanks(10g) still has two x T8 bulbs on it to put one at the front and one at the back.
Look to your hearts content but I'd think about two 36" Finnex Fugaray Planted + lights
on a 40B tank. The right PAR AND spectrum for med light in it/w good coverage all
around the tank.
As far as T5 is concerned I'll say one thing and move on from there.
95% of all who enter the Aquascaping contest have T5 lights on their tanks.
Catalina lighting will custom build a T5 light fixture for you that has two T5 bulbs spread apart 9". The LED I suggested will put you in the lower end of the med range. With two of them.
This light will put you in the higher end of the med range or just into the high end range. They have a three bulb T5 fixture as well as a four bulb fixture. They simply leave out the parts associated/w the middle bulb in a custom 2 bulb 9" fixture.
Remember what that link said about med and high lighting needing CO2 while your thinking about this. But raising the light up cuts it and it's easier to cut than to add more.