What is HQ Player? how does one add it to their system? is it an add-on module?
Is it only for DSD lovers, or for PCM guys?
Is it for geeks, for whom the hobby is as much to play with computers as it is to listen to music (and to whom we should all be thankful for as they are early adopters that help push things forward), or can regular guys who could care less about computer logic use it easily to bring better musical experiences?
HQPlayer is an upsampling multichannel audio player. It's a very high quality upsampler that allows you to select from many high-quality filters for performing upsampling. You may want to do this to bypass the upsampling normally performed by your DAC. Software-based upsampling on a higher-end computer is regarded as superior to that performed by DAC chips, which in comparison are vastly underpowered. Also, the filter(s) supplied by the DAC are fixed, and HQPlayer offers many more that may be more to your liking.
Note that all DACS essentially perform upsampling internally.
HQPlayer is a standalone player that you install like any other program on your OS (it is not an add-on module). While many people (myself included) use HQPlayer to upsample all content to DSD, it also handles PCM content just fine.
There are many forums/posts that you can Google to learn more, as well as going directly to Jussi's site (the author of HQPlayer) to try for free for a few weeks to see if you'd like to purchase it:
Signalist HQPlayer
I regard it as the highest quality player you can get. It's user interface is not as polished as some of the others, but it integrates nicely with Roon which you can use as a front end and this is the way that a lot of people are using it.