You have received very good advice. I have most of the calibers mentioned and shoot them all. Here would be my picks:
Short Action: 6.5 Creedmoor, 6.5 PRC, 260, 7mm-08, 308
Long Actions: 6.5-284, 25-06, 270, 280
Since you have a long action 7 Mag I would pick from the short action calibers to round out your collection. I shoot and love the 7mm-08. It is highly accurate with a great variety of factory offerings. It has sufficient power to easily take deer at your indicated max of 500 yards. Hard to beat a 7mm-08 for an all around deer rifle.
Good luck with your selection. Hard to go wrong with anything suggested so far.