Here's some stuff I have been mucking around with since WinAHX has a tendency to play some AHX tunes completely wrong. This lib is based on Xeron/IRIS's official code, straight from the official HivelyTracker replayer sources. CPU usage of the library is very small too (around 0-4% on a E2200 dual core).
The lib is public domain and is built with MSVC6. Included is the source code, some example tunes, as well as bindings for PureBasic (thanks go to eNeRGy/dAWN for those!)
Sure, for 4k intros this might be useless, but for cracktros/general demos, it should be enough