Resurrecting an old thread here but I was keen to have my Touch play music in my car.
Picked up this
adapter. It's the YC A300 and it runs $10 CDN. You can find it at other sites, I'm just using the link with which I purchased the item.
It's OEM HTC.
It has 2.5 & 3.5 mm jacks, the HTC USB power input, the HTC headset input...pretty much everything you need AND music - on the 3.5 mm jack at least - was in stereo on BOTH channels in my car. yay!
Just query HTC YC A300 in google/bing/yahoo/whatever and you won't be disappointed when you hook up your Touch in your car...provided you have a stereo with a 3.5mm input. heh.
sincerely,
MT