Spectrapure, BRS, The Filter Guys, Buckeye Hydro are all good. If you are on city water, then you need to check their website and see if they have a current water quality report. You need to know if they use chloramines. If they do then you will need to go with a system with 2 carbon blocks to make sure no chloramines get thru to the RO membrane. If just chlorine then a 4 stage unit is probably going to be fine. You also need to make sure you have the water pressure to run one. You really need to be above 40psi but 50 or 60 is much better. If you are not then a booster pump may be required or an adjustment to the water pressure valve at your house.
The 75/90 gallon units seem to be the most common. You can fill a 5 gallon jug in 60 to 90 minutes depending on water temp and pressure.
Prefilter cartridges are recommended to be changed every 6 months. If you want to be precise, you can have them hooked up to a water pressure gauge and change them once the water pressure starts to drop off. RO membrane should last 3 to 5+ years. The di resin just depends on the amount of tds coming out after the RO membrane and the amount of CO2 in the water and of course how much water you are producing.
