Im doing exactly the same... have a 6X4 shed at the moment with everything piled up.. games in the house and games down the side of the house... games everywhere!

Planning to make an L shape shed by adding a 6 X 3 to it ( pulls up 800mm short of where the plans say the sewerage pipe is even though I KNOW its 1M back from there).
This will give me a 9M X 6M along the outside edge with bar at the end opening onto the gazebo where one can sit, relax and pour a beer off tap.

If I cant fit everything into that space, then I need to sell some off cos its impossible to go bigger!