ragvette:
You can't compare wattage from T5 to PC because it doesn't work. T5 are much more effective in lighting then PC so you can't compare watts for watts. The 5 watts per gallon is sort of basic rule but you really need to go by what your going to stock in the tank and how deep your tank is.
I know you ruled out MH but I would re-think that. I'm a MH die hard and thinking of converting my 20gal Nano tank from PC to MH by using the JBJ fixture. See the JBJ fixture here. I still need to reseach the fixture before dumping the money into it but it would look really cool on the 20gal.
Hope this helps.
A t5 is nicer then a pc ONLY if the bulbs have ther Owen reflector. Other wise pc` s are better. I have a 44 gal. pent. . I put down some base rock, then a big branch of elk horn, than a flat rock, to bring the corals up to the light. looks sweet!

P. s. I have evrey thing in this tank but sps.. two 65 watt pc and two 20 watt no`s are all that is on the tank.