YouAmp comes with almost all the modern features demanded by the users nowadays and since it's written in GTK+, it integrates with Gnome easily as well.
Some of the main features...
*. Fully supports managing large albums.
*. Tag editing (you know, editing album, year, artist, etc information right into the audio files themselves).
*. Gain audio volume (according to the developer it has feature called "smart gain", meaning that depending on the characteristics of the file that's being playing, YouAmp will make automatic adjustments without distorting the overall audio output quality).
*. last.fm integration.
*. Zero gaps between playback (no delays while playing between files).
*. Uses the Gstreamer framework. So any audio file Gstreamer "understands", yep, YouAmp plays them.
*. Drag-n-drop support.
*. The GUI is pretty straight forward, easy to understand.
If you've installed Ubuntu then you can easily install YouAmp by using a PPA channel. To do that, as usual, open your Terminal and issue the below command.
sudo add-apt-repository ppa:rojtberg/youamp
sudo apt-get update
sudo apt-get install youamp