My 18G Mk2 has been sitting in my living room for about a week now, as I work up the nerve (and buy other components) to install it into my '00 A4 (non-bose, 2.8qms). I plan on doing the install myself, with the help of some friends. :)

I'll be installing it above a Blaupunkt Toronto headunit for supplying radio and CD to the aux.
My top candidates for an amp are currently either Cadence or Xtant.
I can post an update when I've made some progress actually installing, if you're interested.

Oh, and if you don't know about it, you might give a glance through the Audio forum on audiworld.com. They've got some FAQs on general Audi installation.