New to SW - taking my time

So, I'm slowly accumulating what I need to set up a new SW tank, I've still got a few questions, but I'm figuring out what I want as I go. I've had freshwater tanks for a while, but this is my first go at a SW tank.

I've got a:

75g All-Glass tank
--and--
30g Long (for sump below)

I bought a 2nd hand external overflow (650 GPH)

& was given a:
Via Aqua Multi-skimmer with 5w UV (& Protein Skimmer)
--and--
an Emperor 400 double bio wheel
--and I already had--
an Emperor 280 Bio wheel


& am in the process of setting up the sump.

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I guess my current question is more along the lines of whether it is possible to over filter the water??

I was planning on constructing the sump with a pre-filter box, a pair of baffles, a refugium area & a return pump box.

I was planning on using a submersible pump. but am not sure what kind/size to use. Obviously I don't want something pumping up faster than it will return.

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Perhaps you can answere these questions as a start

Thanks in advance.

Rich

I was planning on using live rock, though it is pretty expensive in PA. Like, i said, I'm taking my time. . .

I guess as per the submersible pump, I meant as a return from my sump. . .

Ok ok, i guess there are divergent view on just about everything.

What kind of return pump do I need? Can I jsut use a big powerhead, or do I need to get a 500 - 600 GPH pump from the sump.

This may be a stupid quesiton, I dunno.

Rich