iPhone 5 Car audio (?)

Any rallly good suggestions for hooking up to my car audio... I've no auxiliary input on factory stereo and want to keep factory stereo. What are some of my best options for really good sound quality, and hopefully easy of hard installation if choosen. It seems to me the FM transmitters made from 10 years ago sound really good (had one, no more) and todays transmitters sound horrible?

Cheers!

STRAY