It really depends on the type plants you have. Some require much more light than others. If you are going to upgrade, I would suggest getting as much light as you can, likethis. That is what I have on my 75 gallon and also, that is the cheapest place I have found online for lights. I bought mine from Big Als for $24 more but that was before I found this site. That particular light has 2 switches. If you wanted to you could only run 2 of the 65s for 130 watts or you can run them both. If you get it and run only 2 though, make sure you are using the switch that runs the fans.
/www.marinedepot.com/md_viewItem.asp?idproduct=CU01006
