Just wondering if this is what I need. 2001 e39 540 with DSP. Appears to have the 3 pin connector and small coax. No CD changer. Thanks!

http://www.pcmall.com/pcmall/shop/detail.asp?dpno=7097206&Redir=1&description=Dice%20Electronics-BMW%20DSP%20Kit%20for%20iPod-MP3%20Players%20&%20Accessories

After further research, it appears this is needed in addition to the actual integration unit. Is this what adapts the normal DICE kit to my DSP system with 3 pin connector and coax?

After further research, it appears this is needed in addition to the actual integration unit. Is this what adapts the normal DICE kit to my DSP system with 3 pin connector and coax?

That's only part of the package - This is the kit you'll need, the link you have is only for the DSP adapter:

DICE iPod Integration Kit for BMW - DSP
http://www.europeanautosource.com/product_info.php?&products_id=284

This includes the DSP adapter required for your specific configuration. Expect steering wheel control, iPod charging and text display after installation!

Does it have an aux in so I can run other mp3 players (like my Treo)?

EDIT: I read the description. it looks like I can run my Treo's mp3 player.

Does it have an aux in so I can run other mp3 players (like my Treo)?

EDIT: I read the description. it looks like I can run my Treo's mp3 player.

Yes sir, you will only need the cable to connect the treo to the DICE.

However, I'm sure the steering wheel controls won't function except with an iPod.

However, I'm sure the steering wheel controls won't function except with an iPod.

Not with AUX, this is only an audio input. You will need a DICE/iPod for full integration.