In_shore - For testing, I would start with standard redbook tracks, ones you know well. For most people, redbook is the vast majority of their music. One of the advantages of the Hugo is its ability to play 16/44. Since you have a SACD player, try some SACDs that also have redbook versions on them, assuming your player plays that hybrid format. They are not always the same mastering, so you have to be a little careful, but it is a place to start for comparison.
Downloading hi rez is always a bit of a crap shoot, depending on the mastering. Some of it is remastered from the original tapes with real care and it can be very good. Other is hardly better than the redbook. I would start with music you already have and know well and look for a high rez version of that.
If you are at all technical, I would also suggest using a program to display the frequency spectrum above 20 KHz. You can use Audacity or, I use a little free program call Spek. That will show you if there is really any content in the higher frequencies. If not, it may be the original source did not have any high end content or it may be the high rez is really just an up-sampled redbook.
JRiver Media Center has the capability of converting PCM to DSD and vice versa. It can be a good way to compare PCM and DSD since you know the source is the same. It will even do the conversion on the fly, although going PCM to DSD does take a pretty hefty CPU. Otherwise, you can just use it to convert to a new file.
It is pretty easy to get started with PC audio if you want to go that route. All you need is a PC with a USB out and a software player like JRiver. Connect the PC to a USB DAC and you should be good to go. JRiver takes a little time to set up. You can start with a Schit Modi for PCM or a Schit Loki for DSD for not much money. The Schit Bifrost with USB is more money, but goes up to 24/192, versus 24/96 for the Modi. I would take it slow rather than jumping in with the "ultimate" system.
If you are not used to dealing with computer programs it can be a little daunting. Dedicated systems like the Sony HAP-z1es are a good option for people who do not want to deal with the computer aspects.
Good luck.