After proper load of network driver, there is still one thing to do in Solaris + qemu – audio is defunct. According to Solaris HCL, audio1371 is for es1370 hardware (pci1274,5000). You can obtain a copy of audio drivers from tools.de site. After bunzipping, you can pkgadd -d it. Note, that you need only TOOLSSbpro driver, so that you may tell the installer not to install all the drivers from the package.
The next obvoius thing is to add_drv -i '"pci1274,5000"' audio1371, touch /reconfigure and reboot. Enjoy the audio :).