Okay, WinUAE is working great except:
1. I only have sound in games, not workbench
2. For some reason, I can't setup the keyboard for game usage....not sure why
I would like to play mp3's from Amplifier in Workbench 3.9 etc.
This is just a guess, but check your AHI settings. Games don't use that API but Amplifier may.
I don't use 3.9 so maybe someone else knows more.