I use to run 75 and 95 w tubes until about 1998 when I added some more 8' fixtures and the ballasts were rated for two 60w tubes in them. I think I may have a few higher wattage lites still but for the most part they have been replaced with 60 w tubes over time as they are the only tubes I have purchased in a number of years. The last 3 or 4 cases of lamps came from Sam's Club - GE's @ about 3.70 per.
If you intend to use a higher wattage perhaps a different balast will be required - I don't know.