How low poly are you looking for it to be? If the Armory pep file is still too high definition, have a look at the foam files - they're generally less complex than pep files (though in this case, it actually looks like the one labled for pep is less complex, just by looking at the preview):
This is a comprehensive zip file including numerous files from multiple artists. Contents of zip-file: halo-4-mjolnir-gen2-mark-vi-master-chief-boot.pdo Modeler: Master Builder Commissioned by MikyVengeance...
www.405th.com
If you know how to unfold files, you can take a high quality model into Blender, then run the "decimate geometry" modifier. This is an easy way to reduce poly count whilst still having fidelity on how much it removes details, though you might end up with a combination of quads and tris (AKA four and three sided faces). There are ways to fix that though.