I am looking to buy a 5-7 stage RO/DI for my reef tank. Right now I have a 3 stage and I do not think my water is pure enough. Can anyone recommend a top of the line RO/DI unit with 5-7 stages? I am looking to spend around $300 or less. I have been told the Extreme Typhoon 3 is good from airwaterice.com. Does anyone have any suggestions? Thanks!