How Can I figure out my Effective Tone Arm Mass??

The Profile arm is an OEM model made by Sumiko in the 1980s, for the lower cost audiophile market. It is a medium mass tonearm, and the bearings are designed for mid-compliance type cartridges. Therefore it would be better matched to the Grado, because the DL103 will chew the bearings up in that arm. You have to have top grade bearings with close tolerance adjustment for a 103. However, it may be not be the greatest match with the Grado either. It could hum because the Systemdek has the motor under the platter, which is known to induce hum in Grado cartridges. I'd suggest a Goldring 1042 or a Dynavector 10x4 or 10x5 for that tonearm.

The Systemdek was a pretty good table for the money, but they have been out of business for a long time. The newer Audio Note turntables seem to be a clone of the old Systemdek, and I suppose it is possible that even some parts may be interchangeable, but I'm not sure about that.

When it is time for you to upgrade, then I recommend doing it in the proper order of importance: table, arm, cartridge.

If you'd like, you can contact me when the time comes, and I'll make some suggestions.