Hello .. I have an alpine 9835 headunit i will be installing in my TSX ... is it possible to use connect the AUX somehow to get volume / track switching via the steering wheel controls??

if so what do I need to purchased or how is it wired??

 

You are describing a few different possibilities as if they were the same one.

To control an Alpine head unit with the steering wheel controls, use this: http://www.discountcarstereo.com/detail.aspx?ID=110 $60.
This product is for people who have removed their factory head unit.

To add an aftermarket head unit as a source on the AUX input, use this:
http://www.logjamelectronics.com/sounsnhond3.html $100

This is if you are NOT changing the factory amp. The factory radio is the master volume control, and I would NOT use the above steering-wheel control interface.

But to take the factory head unit and add it to your Alpine as an AUX into the Alpine, thus making the Alpine the master volume control, use this:
http://www.logjamelectronics.com/piealpairca.html $25.

This is what I would do if I were changing the factory amp. Then I would use the steering-wheel adapter and have those controls control ONLY the Alpine, not the factory head unit.

Do you have Navi?

 

I don't have NAVI (canada) .. what I am doing it not using the gfactory headunit or amp at all ... I have a Phoenix Gold AMP and subs and I want to control the alpine HU via the steering wheel ... I am just leaving the factory unit in place but it won't work ...

 

In that case just use the first adapter for the steering wheel controls.

You can use the last adaptor for MP3 players, FYI. But Alpine is supposed to have an iPod interface coming out...