I have a VERY modest system. My sources consist of a Sonos and a Squeezebox Touch, both of which pull files off of an NAS. My Preamp is a NAD C162, Dac is an XDA-1, Amp is an Aragon 2004, Speakers are System Audio SA505 bookshelves and my sub is a REL T3. Interconnects and digital cables are from Blue Jeans Cables and speaker cables are Canare 4S11. Not department store, but definitely not high end.
I can definitely tell the difference between hi rez and none hi rez files without much difficulty, most of the time. As mentioned, it depends on the quality of the recording.
I've downloaded some files from HDTracks that left me feeling like I wasted my money and I've downloaded others that made my system sound better than it should.