Here is the unit I bought on e-bay -
AQUA-SAFE MAXIMUS II REVERSE OSMOSIS WATER FILTER - eBay (item 160216241944 end time Mar-12-08 20:00:00 PDT)
The components of all
RO/DI units are made by a couple of manufacturers and sold in bulk to the various venders. There is no need to spend more money than what this unit costs - $100 plus shipping.
Get the 100 gpd unit. When you want water you want it now. Get a Brute trash can and keep 40/50 gallons on hand. I have 4 55 gallon barrels full all the time.
Dick