Usually the GPD rating is based on a 75 psi rating. My 100 GPD unit does about 75 GPD at 64 psi. Also, the clear housings allow you to see if your filters need changing. The cost of white housings is 1/2 that of the clear housings. Also, the extra carbon filter after the DI is mainly for looks. Most sediment filters need to be changed every 500-800 gallons, depending on your water quality. And the carbon is usually exhausted after about 800 gallons. The 5 micron filter will cause the most expensive part of your system, the RO membrane, to wear out quicker. Remember, once you wet the RO membrane, make sure you keep water hooked up to it so it stays wet. If you dont, the membrane will become damaged. All that said, the unit seems like a descent deal, however, I would look for one with clear housings.