depends how much you want to spend, but perhaps a good system-design would include:
*CD headunit: blau
*2-way 6.5" components speakers: are the infinity's components or coaxial speakers?
*4-channel amplifier: channels 1-2 powering front speakers, ch.3-4 'bridged' to power sub
*single 10~12" sub
*sound deadener: cover the front doors and seal over the large service holes to help create an 'enclosure' for the speakers; loose fitting speakers with air leaks = 'thin' sound (no midbass)
