rear speaker impedance with Fisher Price Stock '03 H/U

[pada1462]

I am travelling to the USA in April on business and was planning on picking up some 2" Tang Bang extended range drivers to mount in the headrests.  For example these are the 8ohm units http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-806 currently at a budget breaking   s:wink: :wink: s:wink:   $9 each

I am using the Stock Toyota head unit and currently have some old PC surround sound speakers in each head rest but that means left channel in the passenger seat and right in the driver seat. Planning on stereo pairs in the new setup with a custom built MDF mount.

What I am unsure of is do I need 4x8ohm to wire in parallel (giving 4 ohms per channel I think its this option) or 4x4 ohms to go in series (giving 8 ohms per channel).

Another question is do I go with a poly cone or paper cone set.

Any advice appreciated.