Adding usb audio device causes no sound with flash player on archlinux x86_64 with pulseaudio

Question

I added two USB audio devices (from my broken i686 archlinux) to my x86_64 systemd archlinux, a Logitech webcam/mike and a Logitech mike. After this, no sound from flashplugin, either Firefox 11.2… or Chrome 11.5….

The x86_64 has six HDA_Intel audio devices, two on mainboard (analog and digital) and four on two nvidia video cards, the analog is the one I use…

card 0: NVidia [HDA NVidia], device 0: ALC1200 Analog [ALC1200 Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

⋯as I understand it the default for Flash plugin is '0'

I disabled PulseAudio per ¶Simultaneous Playback Issues commenting out lines in /etc/asound.conf. (I don't use ~/.asoundrc because I am the only user.)

This didn't work so I added these lines to a new file /etc/modprobe.d/alsa.conf…

options snd-hda-intel index=0
options snd-usb-audio index=1

⋯Per here.

After rebooting, sound now worked in the Flash plugins, but when I restored PulseAudio by uncommenting the lines in /etc/asound.conf, the Flash plugin produced no sound again.

So now I am without PulseAudio, which I used to up-mix stereo to 5.1, until I find a fix or workaround, or until the i686 gets working mainboard.

I am looking for a fix or workaround, any suggestions?

From the x86_64 system…

[ljohnson{15:57:27}~]$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: NVidia [HDA NVidia], device 0: ALC1200 Analog [ALC1200 Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 3: ALC1200 Digital [ALC1200 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: NVidia_1 [HDA NVidia], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: NVidia_1 [HDA NVidia], device 7: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: NVidia_1 [HDA NVidia], device 8: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: NVidia_1 [HDA NVidia], device 9: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 3: NVidia_2 [HDA NVidia], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 3: NVidia_2 [HDA NVidia], device 7: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 3: NVidia_2 [HDA NVidia], device 8: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 3: NVidia_2 [HDA NVidia], device 9: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
[ljohnson{15:57:30}~]$ cat /etc/asound.conf
# Use PulseAudio by default
#pcm.!default {
#  type pulse
#  fallback "sysdefault"
#  hint {
#    show on
#    description "Default ALSA Output (currently PulseAudio Sound Server)"
#  }
#}

#ctl.!default {
#  type pulse
#  fallback "sysdefault"
#}

#pcm.upmix51 {
#    type upmix
#    slave.pcm "surround51"
#    delay 15
#    channels 8
#}

#pcm.!default "plug:upmix51"

# vim:set ft=alsaconf:
defaults.pcm.card 0
defaults.pcm.device 0
defaults.ctl.card 0