I have a Pioneer DEH P77MP head unit, Pioneer replacement component front
speakers and Pioneer 2 way speakers in the rear doors of my Alfa 156.

I'd like to help out front speakers by fitting a seperate subwoofer. I'm
happy with the volume, just on the occassions I listen to something with a
lot of bass I get a bit "tzzing" from the speakers and the mid range
disappears a bit.

The two caveats are, I'd like to lose as little boot space as possible and
spend up to £150. If I could fit it myself (I've only swapped components so
far), that would be a bonus. I'm comfortable with an active sub if that's
more appropriate for the budget as it is extremely unlikely I will be
upgrading further.

Cheers!
Simon