if your going to get an fm transmitter you should get belkin as they are the best quality but still cost around 60-80 dollars just pick up an old eurovox unit from ebay or the wreckers. should be cheaper than that.
Have been using the Belkin unit.....along with the ipod it creates a nice little mess in the console.
It will do the job, however, the actual sound quality of the unit is restricted. It should be possible to get FM quality sound from the unit with a S/N ratio of ~70dB and frequency response of 30-15000Hz. The unit I have fails a long way short of this........putting it only just above AM radio quality.
I am in the same quandry.....prefer to keep the stock unit....but no auxilary input.......also not all auxilary inputs are that good either....some being quite noisy.
Looking to buy an IPOD controller unit....(its very fiddly working the ipod while driving.....and dangerous) or even one of the units that has a USB stick input.......should be just as good. Has anyone tried one of these