I the general consensus from people I have been talking to is to use the 6*9 as rear fill (exactly as Wozza Says).
The set up I have decided on will be using all Rainbow components, apart from the sub amp (Alpine) and rear 6*9's (Infinity reference series) ski hatch removed and loads of matting on the front doors to deaden the vibrations.
The Sub enclosure is 1.25 Cuft but the manufacturer says 1cuft is best, is this extra 0.25 cuft going to make a huge difference or should I just baffle out some of the box with screwed in MDF so the internal volume is exactly 1Cuft? Also I have loads of carpet underlay, can this be used to sound proof the tailgate?
Still keeping to £500 budget JUST....