sudo apt-get install amarok --no-install-recommends will download what's only necessary for Amarok to run (only 69MB <-these are the dependencies) and it will use 199MB when installed (which I guess is what you mean).
Amarok will probably never be written in GTK as it's part of KDE.
there is however Listen a GTK based player similar to Amarok.
Listen is an audio player written in Python. Thanks to it, you can easily organize your music collections.
- It supports many features such as Podcasts management, browse
- It provides a direct access to lyrics, lastfm and wikipedia
- It intuitively creates playlists for you by retrieving informations
from lastfm and what you most frequently listen to
And let's not forget Exaile which is also similar to Amarok but to a lesser degree, it's available in the repositories.
sudo apt-get install exaile