It is amplified but probably not in the way you want to be fair, it's a line out that utilises the docks more powerful DAC as compared to the iPod.
Have you thought about making/buying a CMoy headphone amp and attaching it to one of these docks? I've made a few of them in the past and they're very easy to make and compact too, they can be mains or battery powered and only cost about Ã‚Â£20 to make.
EDIT: I found this on amazon: http://www.amazon.co.uk/FiiO-Desktop-He ... B004M172FY
FiiO have a pretty good rep with i device headphone amps, this one basically looks like it's a CMoy inside (especially with it having an OPA2134 op-amp, the chip itself costs about Ã‚Â£4 lol!) but it might be a good ready built alternative and should certainly sound good if the CMoys I have built using that chip are anything to go by.
Hope this helps mate.