I bought an AquaClear HOB filter from Petsmart to run my ChemiPure Elite in. It's super cheap and works just fine. I can't be bothered to build my own.
I use a phosban reactor for phosphate remover or carbon. I use Drs. Foster and Smiths phosphate remover and Calgon GAC with the filter. I use them separately. I flow water through it at about 150 to 200 gph, not the 40 gph recommended. I fill 3/4 the way up filter, not half or less as recommended.