The sub is i believe a 6.5" driver, if you upgrade to the z5500 the sub is a 10" driver.
Wires too short, and the wires on the 5300 are not speaker wires (they are hardwired to the satellite) so you can't extend them with your own wires.

Since they are still THX certified though you are getting a good product. Just won't pack as much punch as the 5500.

My gf has the 5500's and a friend has the 5300's and I can definitely feel the difference. I own the Z-560's and imo they sound better than the 5300s.