While LAV can do all sorts of stuff you might not care about, installing it and enabling just the compressor is easy.
With regard to using HDMI from a graphics card, if you go to your Sound Properties via the control panel or device manager, there should be an entry like "NVIDIA High Definition Audio" associated with your AVR or display. Select properties, go to enhancements tab, there might be a "Loudness Equalization" option provided by Microsoft. (It's definitely there under Win 10, anyway, but I recall it showing up back in Win 7 or Vista as well.)
Primary (2.1): Thiel CS 1.2 / Velodyne F1000 sub / Adcom GFA-555 Mk2 / Rotel 970BX / Sony CDP-CA9 ES
Secondary (5.1): Paradigm Mini-Monitor v.3 / CC270 v.3 center / ADP-170 v.2 surrounds / SVS SB1000 sub / Marantz SR-6010 / AppleTV + Win7 PC / BenQ BL3200PT