For the money you could get a much better system than ss.
Hmmm. £365 (the cost of the option) would just about cover the labour costs of a decent install, let alone the hardware. Even if you are handy with a screwdriver, soldiering iron and EQ calibration that £ would maybe get you the sound insulation....
If SPL is your bag then off to halfords for the largest sub you can find, will still cost >£300.
If SQ is more important (personal preference), then the most recent install I've heard (in real life, not on the internet!) was in an 15plate Octavia VRS. Hardware included speakers, sub, amps and crucially a DSP because the VAG factory HU/amp has funky EQ. Professionally fitted for approx £1800 Inc vat and fitting. That did sound better than the SS in my leon.
Interested to see people's shopping lists if they can do this for less than the SS option.