I tend to go for 1400, although you could probably get away with 1700. As long as you count in the fact that every player, cosmetic, anything that the server needs to think about, is an edict, just take that number away, and give yourself a few edicts breathing room. 2048 is the maximum source can handle. For reference, entities like logic_relay are NOT edicts, since they aren't server-side, while entities like trigger_hurt, func_door, info_teleport_destination, are edicts since they can move, or change state or do whatever, and the server needs to keep track of that.