Heres the hands free and audio solution I put together... pretty similar...
The hands free "kit" I put together is actually an assembly of individual components I selected, rather than an actual kit.
I use a standard non powered, vent mount holder for the XDA 2s and power the device via a standard car charger. The holder does not have any kind of speaker built in. I am currently using the PPCtechs "16" adaptor, with the 3.5mm side plugged into a cassette sound feeder (have also used it with an FM sound feeder as well) and the 2.5 mm side plugged into a standard 2.5mm mono hands free speaker/mic combo. I have the mic part of this attached to the drivers side door pillar. Then, I have MS Voice Command installed on the XDA, with the "record" button on the XDA mapped to the Voice Command software
So the way it works is as follows.
1. Get into car and place XDA in vent mount holder. Attach car charger and PPCTech # 16 adaptor to XDA.
2. Turn car radio / stereo on and insert casette sound feeder adaptor (you can use a FM Sound Feeder here instead and tune to the appropriate FM station)
3. Hit the XDA "record" button and at the Voice Command prompt say "Play Don Henley" (It's the only CD I have on my SD card right now.. ) The music starts!
4. Then I decide I want to call someone, so, while the music is still playing, I hit the record button again and on the Voice Command prompt say "call Veronica at home". The music stops and the phone dials the number from the contact list.
5. The phone rings and I get her voice mail (she's never at home ) So I hang up and restart the music.
6. Then a call comes in, which interupts the music with the ring tone through the car speakers. I can see who is calling via the XDA screen and hit the "call answer" button on the XDA to answer the call. My car has volume up and down on the steering wheel, so that its pretty convienent to adjust the volume from there.
7. When the call is done, I hit the "call end" button on the XDA and the music starts back up automatically.
It works pretty well. A couple of other things to address your questions.
a. I don't have a speaker built into the XDA holder, so sound coming out there is not an issue for me.
b. The 2.5mm headset side does still have the speaker attached, but sound is not a problem as its so low.
c. I too have not found a (cheap) 2.5mm "mic only". I asked the PPC Tech folks if they had or could recommend one. They did not, but their solution was simple and inexpensive...."we find just cutting of the headphone part off the handsfree works well"!!
The other thing I use and love is PocketMax "PhoneAlarm" (www.pocketmax.net
) As well as some great alarm functions, this app supports various profiles that control, amongst other things, the input and output sound on the PPC mic and speaker. So I set up the "car" profile with a mic sensitivity and audio output that matches the car stereo best. That way there are no big volume changes when switching from say the car radio to the MP3 music on the XDA (BTW, you can also listen to internet radion on the XDA this way too!)
Well there you go, hope that helps