I currently have a Coralife 3 stage unit and need to replace all the filters and membrane but am also considering buying a whole new unit. Since I also have to watch my "reef spending" (it is neverrr ending it seems) I am asking for opinions on replacing my membrane and filters vs buying a better unit. I know that there are lots of supporters of both the filter guys and spectrapure but by the time you add shipping we are talking roughly $200 minimum for most appropriate set ups. Questions: 1) Other than the filters and number of stages, what makes one unit so much better than another? It "looks" to me like it's a matter of hoses going from one chamber to another and more dependant on quality of filters than the housing. Am I missing something here?? ( I will be the first to say I am plumbing impaired.) 2) What is so bad about the cheaper units (such as ebay) if they use descent filters and membranes? 3) Why should I just ditch my present unit and buy a new one? I know that most have more than the 3 stages . If money was no object I wouldn't be thinking about all of this so hard but I just bought all new bulbs for my T5 and ordered a bunch of stuff from the Drs. group buy. Hubby does raise his eyebrows a bit I spend too much all in the same month and I can't say I blame him! Thanks for the input everyone, I'd like as many opinions as I can get here. Most of you have a RO/DI so you must have an opinion!