I use the 75 gpd Typhoon III model here, but with a few extra features, incl before/after TDS meters, 2 pressure tanks (so you can get quick flow for about 5 gals or so) and a pressure meter.
http://www.airwaterice.com/category/1/
A couple things I really like about it are; clear canisters to check on filters, flush and bypass valves (prolongs life of RO memebrane), the meters, separate RO line for drinking water, and the pressure tanks for quick flow (great feature). And the filters are just all standard which you can buy anywhere.
I don't think you need a 7 stage system unless you have really bad water.