RO Unit

[ReEf BoSs]

I need to buy a RO unit where does everyone buy theirs ? As in best price to quality.

Is there really much of a difference from a 3 or 4 or 5 stage unit?
Its only going to be for a nano tank, so i don't think i need all the bells and whistles. I like reliable and simple, not just throwing money on what cost the most.It will be hooked up to a kitchen facet or garden hose depending on my mood and the weather.
Ideally it will only be used twice a month for less than a day each time if that means anything to the life span of filters/membranes good or bad.
Thanks