Large Tank Filtration

Or just keep using your current filters. Use 2 of them as Biofilters(which would need rinsing out once a month). Fill them up with nothing but biomedia and put a sponge prefilter on the intakes. Use the 3rd one as a mechanical/chemical filter and clean it every week.
 
If you really want to reduce to one unit, or atleast 1 main unit, you might take a look at the larger capacity modular filters like Ocean Clear and Pentail http://www.bigalsonline.com/BigAlsUS/ctl3684/cp19168/cl0/modular?viewType=Category which you have to put together but can pick the right sized pumps and custom config it. And with the right options I've heard they can easily filter many hundreds of gallons. I think you can even get a backwash type setup with ocean clears so you dont even have to fully dissasemble them for cleaning.
 
my LFS has got a Fluval Fx5, they look good and... :D go for it
 
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