Depends on how well designed they were in the first place. If the sub was properly designed that woofer was chosen to work in that volume cabinet.
If you really want to get into it you can remove the woofer from the cabinet and measure it to determine the optimal cabinet size. That would require some test gear.
They sell that type of gear and have an active speaker building forum
If you just want to mess around you can try building a larger volume cabinet. You could also try making a much better cabinet of the same internal volume and design. Wood is way better than plastic.
The soundbar probably has less potential for upgrade unless the cabinet is pretty bad.