Not sure what the stereo gurtu is geting in a wad about, but here's what I did:

Have not one .but two Rockford Fosgate amps(one under each seat in my 90
GL) throwing  a total of 6 channels of 75wRMS to a set of Focals and
Nakamichi 6.5" two ways.  I previously(before the upgrade, but still have
them wired through the chip amp in the Sony head unit) had a set of 4
Boston Acoustics cx4 4.5" biaxial speakers I bought(still available at the
dealer I think, but almost always some floating around Ebay for little
money).  They fit right in the stock locations although I would grind off
the stock VW grilles and use them if clearance on the lateral part of the
dash is an issue.

The point of all of this is, I have the aforementioned switch to turn on
the big amps when needed.  Granted, you don't hear the CX 4's when their
bigger brothers are lit up, but you can monkey with the volume control
settings on the head unit and the gain controls on the big amps so you
don't overload the smaller speakers at higher gain settings on the
R/F's.  What this gives you is the ability to switch off the high priced
spread when you don't want the battery drain and the BA speakers draw very
little current and sound about as transparent as any 4" you will find. BTW,
the head unit is a Sony with about 45watts(not RMS) times 4 channels and
has a decent sized heat sink on the back.   With the big system on, it
really sounds like Diana Krall is in the back seat playing her piano(don't
I WISH!!).  Hope that helps.

DM&FS