Upgraded Rear Deck Speakers to 3 1/2

[The Radium King]

hey - bump to this thread. looking to do the same thing. intent would be to get the rear storage shelf, get the 3.5" speaker kit, but add additional speakers to the centre. would want the whole unit to stand alone - that is, no other speakers in the car except for what is installed in the rear shelf (want to use a blutooth amp so that i can pair my phone to the unit when i want music for cruising, and pull the whole thing out when at the track).

so, what would be best for the middle speakers - 3 or 3.5" subwoofers, more 3.5" pioneers, a 4x6 setup or ... ? thanks for any help; this stufff is greek to me.