Apparently plugins available for XMPlay and Foobar2000 are not up to the task of reliably playing back HES files.

It is recommended that you use Mednafen to play back HES files.

I will revision the hes lyceum page tomorrow and I'll include this.
Ive been wanting to include Mednafen in it for a longer period of time actually.

Edit: Okay, I've edited the page, it only needs some research on Audio Overloads' playback accuracy, otherwise I call it done for this revision.

Have a look at it if I missed something http://battleofthebits.com/lyceum/View/hes%20(format)