I have a Titan x2. It says to be bolted down but I don't and it's fine. If you put plate storage on there you are set. With weights and attachments mine is around 600lbs.
I have a rogue sml-2. It isnt bolted and works fine. The only time when having it unbolted might be an issue is when you are reracking the bar after benching since the force of throwing it back onto the jcups can make the rig slide backwards on a bare concrete floor...but if you can have the rear legs up against a wall that solves that problem.