My PC is older, too, but is an I7, Silverlake maybe, with 16GB of RAM. It has been awhile since I checked resource consumption, but Kal and I compared notes on that 1-2 years ago. I seem to recall CPU in the 10-20% range playing a Mch 5.0/.1 DSF file while doing on the fly 176k PCM conversion, bass management in JR, and Dirac Live EQ with USB output. And, my HiDef TV was on as a monitor via HDMI through my AMD GPU. RAM usage was only about 4 GB with 16-bit JR. Overall, loafing, I would say.
I have also occasionally loaded up five or six simultaneous tasks - file copies, extracts from ISO, etc. - while listening as above in Mch. I heard no dropouts or buffering, etc.
Fan or disc noise is inconsequential for me. My PC is in an adjoining room, connected by a 5 meter USB cable through the wall.
Conversion to 96k or 192k is probably sonically inconsequential compared to 88k or 176k.
I do avoid bitstreaming DSD because that does not permit speaker distance correction, bass management or room EQ. Hence, there is some Mch spatial distortion and adverse room effects, especially in the bass, using pure DSD in my setup. My speakers also benefit from bass management to a sub.
Yes, I totally agree about the excellence of Mch listening, and SACD, in spite of its quirks and difficulties, is still the primary source for Mch music. I have built my library and system to enjoy it to its fullest.