sump pump placement

[DocOops]

I posted the following in the main reef board, then found your author section in one of your plumbing articles:

I will be setting up a 180g reef soon and will be locating my chiller outside - plumbed through the wall. I estimate using approximately 20 ft. of 1" (or 1.5"?) PVC and 4 90 degree turns (total to and from the tank/sump). Can I locate the main pump (a GRI 520) outside with the chiller to minimize noise? The tank's going in the family room and my wife wants it to be as quiet as possible.
There would then be a horizontal/slightly downhill run of 10 feet from the drain bulkhead in the sump to the pump outside; my LFS said that would be OK but I seem to remember seeing posts here suggesting that the pump intake should be as close to the drain bulkhead as possible. Why?...the chiller (and pump if possible) would be about 6" lower than the sump so priming shouldn't be an issue. Is cavitation the problem or is there some other issue I need to know about?
(I know this is a lot of flow through the sump; the GRI 520 is rated approximately 1500 gph at 6 ft. head and is pressure-rated. I'm planning an Ecosystem-type refugium/sump, and they recommend 1200 - 1500 gph)

Thanks for any input.