Amplifying/Normalizing the sound to -1 dB is about as high as you can get without either (a) clipping (distortion) or (b) compressing the dynamics.
Compressing dynamics is commonly used on commercial recordings so as to make them sound louder (see Loudness War http://en.wikipedia.org/wiki/Loudness_war ).
Personally I prefer to retain the dynamics and turn up the volume on the amp, but if you want to try dynamic compression, three effects that can help to accomplish that:
- The Compressor effect http://manual.audacityteam.org/manual/help/manual/man/compressor.html
- This “Limiter” plug-in http://wiki.audacityteam.org/wiki/Nyquist_Effect_Plug-ins#Limiter
- Chris’s dynamic compressor https://forum.audacityteam.org/t/chris-capels-dynamic-compressor/20241/1