Ok, I guess I will give you my watts/gal spiel, again.
Watts per gallon is a terrible measure of lighting. What is important is the following:
<ul type="square">[*]Height of tank[*]Distance from lights to water[*]Types of lighting (MH, NO, VHO, PC, Etc)[*]Height of liverock in the tank[*]Lenght and width of tank[*]Reflectors used[*]Intensity of bulbs[*]Spectrum of bulbs[*]Orientation of bulbs[*]Type of livestock you wish to keep
[/list]
Using the term watts/gallon oversimplifies the issue too much.
If you are talking about a standard 55g w/ a 4" sand bed, lots of LR stacked high w/ bulbs 6" off the water and you plan on keeping softies and a couple anemones, and you insist on PC lighting I would suggest the following:
4 x 65W PC Daylight
2 x 65W PC Actinic
If you use 96W PCs, they are 3' long and will not cover the entire length of the tank. You will have dark edges (6" on either side) if you go with the 96W bulbs. I would arrange them like this:
Rear of tank
DDDDDDDDDDDD DDDDDDDDDDDD
AAAAAAAAAAAA AAAAAAAAAAAA
DDDDDDDDDDDD DDDDDDDDDDDD
Front of tank
unless you have your liverock stacked against the back wall, in which case you might consider the actinics up front like this:
Rear of tank
DDDDDDDDDDDD DDDDDDDDDDDD
DDDDDDDDDDDD DDDDDDDDDDDD
AAAAAAAAAAAA AAAAAAAAAAAA
Front of tank
Just my $0.02
Ernie