You can purchase those iPod car kits but they costs several thousands din much like buying an entry Pioneer head unit. I think the most cost efficient way is to still burn your songs on a CD if you're without a iPod support/Aux in HU.
*purplegrape
An iPod isn't an assurance of good quality. Sound quality can only sound as good as its source. Most burned mp3 files range from 128-320kbps. 128kbps is crap.. if you listen to downloaded OPM music coming from Limewire or the net, ito na yun. 320kbps, on the otherhand, is perfectly acceptable na. Pure uncompressed WAV files are still the best (1411kbps) and where can you find these? Rip a genuine CD or download those FLAC/loseless audio albums. Take note that a single song may be somewhere 35mb upwards versus a 5mb mp3 file size.