Steven, as I stated before, the number isn't as important as how fast it recovers after feeding, water changes, etc.
I would expect a tank not running ozone to be in the low 300's.
Example: Lets say your ORP reading is sitting at 300. You feed your fish and the ORP drops to 260. From my experience, your ORP should recover within 4 to 6 hrs or so.
Example #2: Lets say your ORP is at 300. You do a 20% water change and the ORP drops to 250 or so. (Very normal as the ORP of newly mixed salt water is about 220 mv.) I would expect the ORP to be back up to 300 within 8 to 12 hrs or so.
Back to Marcs' Starfire.
