Wet Dry Sump Pump question!?

Ok, I have a wet dry sump/filter now..... I want to buy a new pump for it..... Im looking at 500, 700, 1000 gph pumps..... my wet dry is about 20gal maybe a lil more, and my tank is about 100 gallons.... what pump should I get?? I want to go big, but if I got the 1000gph pump would it work too fast and cause problems overflowing the overflows? Any suggestions comments would be appreciated.

if i were you id look 600-800 gph range. i run 800 gph on my 240 and it works like a dream.

does your 800 have allot of flow?? The lake Im tryin to copy has a strong current, my last tang tank had a sump with a 500gph and a fluval 304.... I really want it to be that strong thats why I was thinking 1000, just dont want a problem with overflowing, or can that even be an issue??? anyone have a problem with having too much flow with there sumps/overflows???

It does flow quite a bit. The drain seems to push out a lot of water

what is the pipe size for the overflow?

output is 3/4, intake is 1".... I think.

im pretty sure 1" handles about 600-1000 gph depending on full siphon or not

im doing the 1000gph pump.... i figure I could always just get a valve to adjust pressure... better too much than not enough.

Check out this link and it might help:
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cool calculaters.... but I think I like allot more flow than what they are recommending.... Ive put way more gph from canister on a 55gal than what they recommend for a 75.... but It might be talking about the bare minimum... which is super cool for beginners that want to know.