I’m also in the process of upgrading my SYSTEMDEK IIX. I bought it nearly 20 years ago and have kept it stock with its Profile 1 tonearm. It came with a Grado Reference wood bodied MM phono cartridge and sounded quite nice. However, the bearings in the tone arm have become worn out, as is the cartridge stylus. I purchased a new old stock Jelco 370 fluid damped tone arm which I will eventually have installed. The Jelco was manufactured in 1984, the same year my IIX was built.
I also need to upgrade the phono cartridge at some point.
The llX can sound quite good when set up properly (hence its nickname "the poor man’s LP12). So I am hoping that it will be the last TT I need.