you can find pc fixtures for home use, and swap out the lamps if you like. i think you can also find ho flourescents and do the same. the big problem comes when you talk about moisture. unless the fixture that you are buying is rated specifically for use in a humid location (it will say this on it) it will VERY quickly rust, corrode, and destruct. the damage can range from your fixtures no longer operating, to your bulbs shattering and spraying glass all over.
there are a couple people i have heard who use normal fixtures and have been lucky thus far, but if you are going to go with the things that you can buy for home use, namely pc and no or ho strips, the price difference really isnt too much from aquarium trade fixtures. personally the possible electrical shock, fire, and destruction of everything in my tank just isnt worth the 30% less that household stuff seems to run.
(BTW I have tried 13 watt desk lamp fixtures, they rusted in less than 2 weeks)
HTH