Help making too quiet sound work on Mac Pro running -STABLE

[George Hartzell]

I have a mac pro running amd64 -STABLE from a week or so ago.  Most
things are working well, but sound's not quite there.

When I plug a set of powered speakers into the headphone jack on the
front of the machine and max the mixer setting and the speakers, I can
just barely hear an mp3 played by mpg123.

I'm loading snd_hda from /boot/loader.conf, and /dev/sndstat tells me:

  FreeBSD Audio Driver (newpcm)
  Installed devices:
  pcm0: <Intel 631x/632xESB High Definition Audio Controller> at memory 0x93100000 irq 23 kld snd_hda [20070619_0045] (1p/1r/1v channels duplex default)

There's a chunk of the dmesg output from a verbose boot at

  http://shrimp.alerce.com/misc/delicious-dmesg

which seems to include all of the pcm info.

What other info can I provide?

g.