its going to be hugely variable depending on brand, amount of kit, fuel etc on board.
As a starter though Humber quote their boats (this is no kit, no engine) as:
6m Ocean Pro = 495 kg
6m Destroyer = 415 kg
5.9m assault = 325 kg
Ribeye claim a 6m rigged with engine etc weight 890 kg
Ribcraft claim their 585 (they don;t list a 6m) weighs 588 kg + engine.