sump

I am making plans to switch my 75 fw over to a reef tank, and I'm currently
looking at filtration. I have 2 options;

1: An Eheim Pro 2320.
    Opinions on this unit for a 75 gallon reef?

2:Sump. I have empy 10 and 20 gallon tanks I can create sumps out of. Would
the ten work? Too small? I would likely be powering it with a Rio pump,
about 550gph.

All opinions appreciated.

-- 
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Billy
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I'm not closed-minded.
You're just wrong.