I just recently researched and bought my first RODI unit and here's my experience:
Other than going local (John) - thefilterguyz, Buckeye Supply, Air Water Ice, SpectraPure(best but expensive), and Purely H20 (Orlando) are considered the popular reputable ones from everything I've read. Ebay ones look cheaper but seem to give you smaller DI cartridges and the RO cartridges take out less stuff (maybe enough but less) making it not so great a deal. There doesn't seem to be a consensus on whether 2 plain (typical) carbon blocks will remove chloramine or not BUT.. the best way to remove chloramine seems to be to use CATALYTIC granular activated carbon (specially treated granular carbon), followed by another carbon block. (also there's a sediment before and a RO and DI after those carbon blocks making it 5 stages).
I was either going to get the chloramine ones from filterguyz or Buckeye but decided on buckeye just because all the canisters and pressure gage were on a single frame and I can easily take it out and hook up to my kitchen sink faucet. It's worked well but I've noticed the RO water has a bit of an aftertaste so I pour it though some carbon before storing. You can add a pressurized tank and faucet to any system to make it easy to use for drinking water or just fill up a 5 gallon jug of RO water like I do.
