There's an embarrassment of riches on Windows for SPC playback; I think most people use Foobar2000 and some plugins. AO exists on Windows basically because I could do it, not because it's better than e.g. a fully loaded Foobar2000 setup. It's not like on Mac/Linux where it's often the only option.
I use Winamp 5.52 + the Alpha II SPC plugin (SNESAmp). Full access to any feature I need for SPCs. NotSoFatso plugin works great for NSFs as well. And very easy access to writing WAVs to disk for playback on any audio device using either the embedded timer info in the SPC/NFS/NFSE or user specified times.
Oh, and this works inside CrossOver in OS X as well without slowdown or crackling sound issues.