I don't believe wav is a stream-able protocol.  The metallic sound is more an artifact of compression than the protocol used.   You might try bumping up the bitrate and/or adding a lowpass filter to strip off the highest  frequencies,  this is commonly done with stream encoders.  I've added a highpass filter to remove PL.  I imagine you could do low pass the same way.   Here's what I use.

outstreamcmd=/bin/sh,-c,/usr/bin/lame --preset cbr 24 --highpass 0.2 -r -m m -s 8 --bitwidth 16 - -  | /usr/bin/ezstream -c /etc/ezstream.xml

Steve