yeah the purewaterclub i did a review on here a while ago. it's cheap as shit AND with the BLUELAB or my other tds/ppm/ec meter it reads zero or like 4-5 ppm which none can measure that accurately anyways so i dont see a single reason to ever buy another unit unless someone finds one cheaper. it works as well as a RO can and it's the cheapest i've found and i've ran a few thousand filtered gallons through one without replacing the filter and still had acceptable water. what more can one ask for?
This is out of your price range, but the GE Merlin uses two RO membranes and produces up to 750g per day. If you look around online you can find them about $350.
I, too, am a PureWaterClub member. Got the 100gpd RO/DI unit, which is 6 stages. Pay attention to the order in which filters and membranes are placed, as well as what's in each stage. I can't remember where I found the information that talks about the different cartridges and how they should be placed, but the PWC unit fit the bill perfectly.
The RO police will start long threads about why one RO unit is better than another. IMO zero PPM's is zero, look for the least expensive, good links already posted.