I fully agree with Levy03.
I wouldn't worry about XLR until you get a pure digital signal out of the iPod first. Then you can deal with XLR balanced (which is a whole other issue that usually isn't as black and white as you might think).
I've used both the Wadia and the Onkyo docks, and they seem to be identical in every system I have used them in, and that also is the experience of others who have compared the two. The Onkyo is more affordable, but difficult to get in the US. Either way, those docks make the iPod compete with very expensive CD transports and should allow your foot to tap. ;)
Have fun....