planning 90g reef for the future

[pufferman]

Switching from a 30g to a 90g will be relatively easy for me as most of the equipment i have on my tank is rated up to 150 gallons. All that i will need to get is additional LR and LS and lighting. I wanted to know if my 30g tank is enough of a sump for the 90 gallon. how do i make my sump partitioned and the water level constant. I will not be hard plumbing this in case of moving or any other circumstance. I was thinking about a ball valve that i found on drfostersmith.com for vinyl tubing. Also at what GPH pump should i get for the sump?

TIA

P-MAN