How about adding an IEC chassis plug? You could put one in and use the 18ga. leads and solder them to the IEC. Would require a dremil tool w/metal cutting wheel. You could then make your own power cord (say 14 guage) and use Pass seymor/Marinco ends. Or...remove existing 18ga. power cord and replace w/16 guage lamp-cord or use Carol Cable 14/16 guage cord. You'll need rubber strain plug/strain relief that could be bought from True Value for around $2.50. You'll use the Carol Cable w/this set-up and make a splice w/the existing 18ga. wire. I've done many times on most of my inexpensive used audio gear. I've been doing this awhile and have experience/practice. Not hard but you have to know what your doing. Does it improve audio performance. I'd say yes it does. But you'll see greater audio improvement by adding better binding posts/rca plugs and rerouting low level wiring away from power wires. (Why are these bundled together?) Lots of little things could be done to improve the sound. If you confident you could do the job well, go for it if you plan on keeping the receiver for many more yrs. Please be careful. Honestly, like the previous member so stated, will not bring that much performance improvement. If you the itch for better 2-ch/stereo sound, look into quality int. amps/seperates. Good Luck!
