Dude...you have no idea! First of all the DI is the one of the most important parts of the system. Second, Kents RO units suck. I have tested water from a friends system with a TDS meter and it was crazy high. I have a 5 stage double DI system from Spectrapure. My sediment filter is 1/2 micron. Yours is at least 1 micron. My water reads less than 1 on a TDS meter. You can't beat it. Water quality is priority one in a reef tank.
Spectrapure is the best period. Also if you have chloramines, then you will deffinately want DI. That Kent system will not remove the amonia from chloramines. Did you hear that...I said AMONIA. My second DI cartridge is the AR (amonia removal).
Please don't..the money you save here, you will loose 10 times over in the future.