Most commercial audio CDs have been mastered using heavy
compression and even clipping to raise the AVERAGE or RMS
level of the audio. "Normalizing" the wav file helps but
if the audio has large peaks relative to the average level
the overall volume will still be low. Use the compressor
in Sonic Foundry and don't be afraid of a little clipping.
If the clipping is only on short peaks you won't hear it.

This approach, by the way, is typical for "popular" music -
you wouldn't want to use it on "classical" music CD where
the intent is to preserve the dynamic range.

Jeff Rippe
Rocksonics Professional Audio