With regards to your rear speakers, i wouldn't use the factory locations, have a look at them, you'll notice that they are all the way right back and fire towards the windscreen. That's factory audio for you, and is less than ideal when chasing good sound quality. If your going to replace your rears, personally i recommend mounting them on the front section on the parcel shelf, there's a deep grove underneath it, you'll see if you remove your shelf, this space generally allows sufficient depth for a decent 6-6.5 inch speaker, and will give far better clarity, and will only require the cutting of the pressed fibre shelf only... a 6x9 however will genereally require a spacer to fit though, depending on it's mounting depth..If your picky and you don't want to modify your front door trims, (VR/VS pods dont match with the VN/VP colour theme) then there are plenty of decent 4 inch speakers out there,(FOCAL!!) will sound pretty decent, there are some advantages to be had, using the factory location compared to a pod, is the dash mount will fire directly and upwards towards you, while the pods will project the sound down around your legs..Once that's all in a properly amplified and tuned, you'll notice a huge difference..Also being a VP, it's factory sound insulation leaves a lot to the imagination. You'll find with a decent setup, you will get a lot of resonating from the boot and rear shelf, which can be overcome with sound sound deadning material ( such as Dynamat) and some undercarpet underlay.
