I highly recommend that you read Hoppy's Article on lighting with PAR, I found it very useful. I currently have 2 low tech 29 gallon set ups and I am using 2 T5NO bulbs on one of them and a single T5HO on the other.
Are you going to run CO2? That will definitely make a difference in your lighting choice.
Just read the information in Hoppy's post (one of the articles in the sticky above) and follow his recommendations.