Hello Gare0440,

I believe that DutchPimp recently went to a T5 Quantum fixture and I think he is very happy with it. Maybe he'll stop by here and can give you his opinion of it.

As Gypski pointed out, lumen output is pretty much the same for any T5 HO fixture, regardless of how efficent the mfg says thier ballast is.

Looking at the specs of Hydro-Farm vs Quantum, I can tell you the specs for the HF are more "honest". HF says there 8 lamp fixture uses 454watts and Q says there fixture uses 432watts. Hmmmm....8 lamps @54w/lamp is 432w that means HF recognizes the ballast uses abt 22watts, while Q would have you believe their ballast uses nothing. That's just not possible, I'm sure if you checked it out you would find the Q really uses more then 432w.
Also, you are mistaken that the Q bad-boy is fan cooled. It clearly states the fixture and reflectors are "vented" meaning they have holes or slots to vent.

You can find fan cooled fixtures, check out what the aquarium hobbyist's use.
You can also find co's that have fans designed to be used with T5s. On the subject of aquarium T5s....
Check out Ice Cap's line of ballasts for use with floros, their ballast drives T5s to VHO levels, meaning a 4' 54wHO bulb is driven to 85watts. It almost doubles the lumen output without doubleing the wattage. You can even use cheaper NO (normal output) bulbs and drive them to VHO. (BUT you can not mix HO and NO bulbs)

Before someone jumps in with "but it shortens bulb life" I will tell you yes it does. But so what? I tend to use the cheaper NO bulbs and change them out every 6 months or upon death, whichever comes first.
OM