Novice question

New to the website and probably way out of my league but will appreciate any help. I’m 60 years old and was lucky enough when I was young to have my folks give me,over time, a Yamaha CR-1020 receiver/integrated amp, small Advent speakers, and a pretty good Technics turntable. I felt pretty lucky. That rig lasted a long time but I eventually (and probably foolishly) moved on and turned to cheaper/modern stuff when they wore out. I also turned to cds and digital along the way. A couple years ago, probably out of nostalgia, I bought a Yamaha M85 power amp, original large Advents (stacked) and a pretty decent modern Yamaha CD player. I also added an Audioengine B1 Bluetooth player for times when that’s a preference.  A couple questions—for a pre/control amp should I just find a Yamaha C85 or C80? Or would something else be better? I have a Yamaha C-4 but it has issues and will cost about $600 to restore. That’s a lot of money for me. Would that be a smart investment and good match for the M85? Also, my system sounds good to me and I don’t have thousands of dollars to spend but should I go another direction? I’m also using cheap cables and speaker wire—will higher priced cables make a notable difference difference w/the same components? I’m obviously a novice here but appreciate any sincere advice and guidance. Thanks. I enjoy the website and discussions.