Leon Sub

[pstables]

I'm toying with the idea of buying a sub for my Leon Cupra (with Aura head unit).

Empire Direct have a Sony XSAW200X Active Sub for £132:

http://www.empiredirect.co.uk/productdetailsnew.asp?MODELCODE=SON-XSAW200X

Is this any good?
Will I notice much difference?
How do I wire it in to my head unit.

Thanks in advance,
Paul