Just tried your test on my Win 8.1 64 system. When DPS GUI is on the desktop and not playing media on the Home screen, CPU usage is in the 1.5% to 2.4% range. It appears to fluctuate when the memory usage changes. When on the Settings screen, CPU usage is in the 0% to .3% range.
When DPS is processing media, on the Home screen, CPU usage is in the 2.4% to 3.5% range. On the Settings screen, CPU usage is in the .9% to 2.1% range.
When the GUI is not on the desktop, and playing media, CPU usage is in the .8% to 2.4% range. When no media is playing, CPU usage is in the 0% to 1.5% range.
My CPU usage readings are lower than yours, but we probably have different processors. Mine is an i7-4770K.
UPDATE: Just saw your second post and did the same test. DPS CPU usage is in the 0% to 1% range and RAM is locked at 17.9MB with no fluctuation at all.
When I stopped playing media, CPU usage is in the 0% to .5% range. RAM dropped to 17.8MB.
When I opened the GUI to the desktop, the CPU and RAM utilization spiked back up as noted previously.
ANOTHER UPDATE: I closed the GUI and noticed RAM usage climbed to 960MB, then dropped down to 30MB, then repeated the same pattern again. I opened the GUI on the desktop again, and the memory usage dropped back to the lower ranges reported earlier. Closed the GUI again and the high memory usage repeated itself. Terminating and restarting DPS without opening the GUI went back to a steady 17.9MB RAM usage.