Lets talk light for a minute.
Now light coming from a globe isnt dependant on the power is uses ie a 25W T5 isnt giving out 25Watts of light this is meaningless as light is measured by the amount of photons (packets of light) per amount of time another measure is lumans output
This equivalent part is what gets me 1Watt isnt the light its putting out its the power its consuming.
most T4 lights are approximatly 60-70 lumans per watt (some new ones up to 90lumans/watt)
most T5 are around 70-80
CFL are around 50-65 but are cheap usually in comparison
MH are aroudd 60-100ish (higher wattagaes are more efficient but cost more to run)
LED are 110-136lumans per watt (these have their own draw backs aswell)
Geneal rule for scrubbing
0.5 actual (not equivalent) fluorescent watts per gallon MINIMUM.
1.0 actual (not equivalent) fluorescent watts per gallon for HIGH filtering.
now watts is what the light unit uses to gennerate its light output which for light is lumans (packets of light per unit time) which is what we are interested in.
So in the guide it says not equivalent fluroesscent watt and as far as i can tell you based it on T5 lighting and that you cant have too much light essentially but cost of running lights and effective scrubbing are two very different things.
Therefore assuming 70-80lumans per watt we are using T5's as the SM100 puts out 7-8000lumans as its 100watt total. (assuming good reflectors so that close to 100% of the light emitted is directed to the screen)
This is for high filtering (1W per square inch)
The screen is 200cubic inches so essentially we have 40 lumans per square inch of screen.
2X100 square inches = 200 inches^2 total
8000/200 = 40 lumans/square inch.
so 40 lumans per squareinch of screen has been found to be high level of scrubbing by your design which speaks for itself in effectivness.
Now lets look at it from a tank volume point of view. tank volume is 100 gallons so thats an easy 70-80 lumans per gallon for good filtering
common sizes of tank and light needs
28 gal needs 2000lumans at 1.5inches away form screen
50 gal needs 3500 lumans at 1.5inches
100gal needs 7000 lumans at 1.5inches.
150gal needs 10500 lumans at 1.5 inches .
500gal needs 35,000 lumans at 1.5inches.
Lets look at Lux or light power per unit area
Now lux (SI) or footcandle (IMperial) is the light power per unit area.
40 lumans on 1 square inch (0.000625m^2) is 64,000 lux (close to 6000 foot candle) as a rough guide to the amount of light you should be aiming for for good filtering. As a guide direct sulight starts at 32,000 lux and goes up to 130,000lux so the light needed is around 1/2 the power of the sun ( this doesnt include infared light which is the power of the sun that we feel its the sun in light intensity)
Lux depends on the area we are illuminating. Decent reflectors are a way to focus the light but they can only do so much so placing the light source close to the screen is a good way to increase effective irridance. look at reflectors that throw the light to the entire screen surface while being as close as possible to the screen to give uniform light distribution. but being in this 1-2inch range is where the aquerium reflectors ad DIY reflectors are going to be able to throw most of the light effectivly.
I hope this helps a little to the knowledge of light needs and hope it helps future development of lighting or design.