Instead of a slight improvement with a booster pump, you might want to consider using these. I have two of them plumbed into my RO/DI system and have plenty of reserve water on hand for things like filling 5 gallon jugs. My 75 gpd system at 65 PSI fills the tanks back up in a couple hours.
http://www.airwaterice.com/product/P...2-Gallons.html