The ultimate Denon 103 upgrade is the Audiomusikraft First Series cartridge/shell. I got the Bronze shell weighing in at 21 gms and its extremely good. Has made it in Stereophile's Class A cartridges for a number of years. I replaced the original103 stylus with a VAS Audio 103R retipped with the boron cantilever and microridge stylus and it sounds spectacular. First time buyers have to buy the shell w/ the cartridge - after that, just replace the cantilever and stylus as it wears out. No need to wait for lengthy retips and relatively cheap compared to performance. I use it w my Kuzma 4P (11) - make sure that your tonearm can handle the weight. I do not see a need to buy expensive cartridges anymore. Link to site below - also check out Stereophile's Recommended Components for the last few years.
Bronze (Br) - First Series Cartridges - Audio MusiKraft
Bronze (Br) - First Series Cartridges - Audio MusiKraft