Rescue! 2.0.5, in combination with the Sound Manager 3.0 extension, should be enough for most users to enjoy multiple channels of sound.
If you're having trouble getting the sounds to play in Rescue! 2.0.5, here's a few things you can try before writing me.
1) If you're using System 7.1.2 or earlier, ensure that Apple's Sound Manager 3.0 extension is installed in your Extensions folder. (Note that System 7.5 comes preconfigured with the latest Sound Manager.)
2) If that doesn't work, quit Rescue! and restart it, then select "Single Channel Output" from the Options menu.
3) Remember that users of old Macs like the Plus and SE have no choice but to use Single Channel Output due to hardware limitations.
If you still can't get the sounds to play, write or e-mail me and I'll see what I can do to help.