2006 Highlander factory upgrade options?

[zzoinks]

All,
We just bought an '06 Highlander, 4Cyl, Fwd. Pretty much a base model, I think the only option was privacy glass. It currently has the single CD/tape combo head unit. It's my wife's car, and she isn't into aftermarket stuff. However, her previous car had a 6-disc in dash changer and steering wheel audio controls. I added a Sirius starmate tuner, and she was happy.

I'd like to get the Highlander to the same level. From what I've seen so far, it looks like there's JBL and non-JBL systems. Am I correct that all JBL head units are preamp only, requiring an additional amp?

More questions:
What are my options for 6 disc in-dash changers? (Model numbers would help)
How hard and expensive is it to add factory steering wheel controls? Does it require a different wheel, or just plugs into something on the existing wheel?
Is this a good solution for adding an Aux input to the factory head unit, and will it work with any changers I might add? http://www.logjamelectronics.com/pietoy03aux.html
Do the JBL and non-JBL systems use the same speakers, or are those different also?
Finally, does anyone have any of the above equipment for sale?

Sorry for the long first post, but this is my first experience with Toyotas!

Thanks,
-Brett.

[zzoinks]

I installed the Sirius tuner temporarily last night using a cassette adapter. I ordered the PIE aux adapter this morning.

If it helps answer the above questions, my existing head unit is part number "86120 - 52241".

Thanks,
-Brett.