Thank youthe two easiest ways I have found is to flash a kernel such as courtts one which has an audio boost mixed in
http://xdaforums.com/showthread.php?t=849002
and/or download 'zedge' from the market which has tens of thousands of ringtones (and wallpapers) and many of them have been recorded really loud (so loud that I have to actually turn the volume down...!)