Oh dear. The world read that last question and said 'Oh Noooo, here we go' Llj is cringing now awaiting my reply. lol
If you ask me about CFs (or indeed T5HO) you risk having a huge rant in your thread

So here you go. A useful rant though.
You are one of the fortunate ones who asks the question BEFORE doing anything. Most ask why they are struggling under their new super T5HO lamps etc.
Lets just say linear tubes are better than CF

and the more tubes to get the same wattage the better. Steer clear of T5HO if you can. better to use T8NO or T5NO (NO = Normal Output) to get you 55-60W and then you can space them better.
You could get 3 x T5NO 21W rather than 2 x T5HO 30W then space them equally front to back. NO lights last longer are more efficient than HO lights, have more light per W too
T5NO are quite limited in choice which is why I normally suggest T8. Purely because of tube availability. IF you get the spacing/spread correct you will only need 40W to knock spots off 55W of PC not in terms of actual light. In terms of spreading it out and you will notice the difference from your plants. Therefore don't buy a retail setup as they will be squeezing tubes into the centre of a luminaire. try and retrofit it and then you can get as much as possible from the lights and therefore either have more light and or be able to use less light to get the same/better results.
Oh and why are CFs so bad. Spacing you have 55W tightly packed in one position over the centre of the tank. Huge intense hot spot directly underneath and low intensity away from the tube. If you then say have 3 x 18W T8 the huge intense hotspots will be replaced by 3 not too intense hotspots and the areas not directly (as the crow flies) beneath the tubes will be much closer in terms of PAR to the hotspots

Its what I call spread/coverage and will become (I am determined) a key feature in the future.
Told ya so, Don't ask me light questions. lol
AC