Late to the party here, and I agree with the general thrust that your table is capable of delivering far better results than you're getting out of it with the arm and cartridge you presently have. The 103 is a good cartridge, but not a great one and the Sumiko arm is in the same class. Your friend's arm and cart are truly major league.
Further, @mijostyn and @bkeske are correct. I have a 1984 Sapphire purchased new off the dealer floor and have found it to be a very easy table to work on that is superbly reliable. I did have it updated by Sota about 10 years ago with a Series V platter, new springs and composite armboard to fit a Graham Phantom. I'd looked at the TriPlanar and even spoke to Tri Ma about a Series III he'd posted here. I'd also considered SME, Reed, Kuzma, JMW and even attempted a rebuild of my original Magnepan Unitrac 1 that didn't work out. For my needs, the Graham was the best compromise. I'd sold SME for a few years and really liked them, but strongly preferred VTA on-the-fly. The JMW and TriPlanar wouldn't fit without modification, and I frankly felt the JMW was not made to a standard I found acceptable. The 9" sized Graham, SME, Reed and Kuzma are all essentially drop-in replacements if you purchase a new armboard from Sota for the tonearm you choose. Sota can guide you very effectively there and they've been doing it for a long time.
For a cartridge, there are dozens of higher performance choices that a better arm can really take advantage of. I personally have a preference for Dynavector, and have also experienced stellar results with Ortofon, Koetsu and Lyra.
Because there are so many alternatives, the best thing you can do is be patient and research what's available. Once you feel comfortable with your knowledge base, pick a budget and build in a bit of wiggle room. World-class arms can often be had for ~$2K second-hand and half that for a brand-new superior cartridge. As some have mentioned, you can also look into a more capable pre if you wish. No matter what you do, just remember that you are into this to please yourself and time is your friend in that quest. Keep that in mind and you'll do fine.