recommendation for a high end analog system

As another Sota owner I think bkeske has the right idea. Your arm is a little on the heavy side. Something a little lighter would be nice along with a better cartridge. Rauliruegas is right there. As a Sound Labs owner you will appreciate a cartridge with more detail, the Lyras, Ortofon Windfeld Ti, Soundsmith Sussurro  or Voice. As for tonearms, you are limited to 9" arms that will fit that include my favorite The Schroder CB but also the Reed 2G, the Kuma 4 Point 9, The SME IV or V, Origin Live arms and others. The current Tri-Planar arms will not fit without significant modification to the plinth. The Schroder will fit like a glove and is hard to beat at any price. If you call Sota with your turntable's serial number they will send you a new arm board. After that deal with the Phono stage if the sound needs more improvement. 

@mijostyn

That Sumiko is a rebadged Jelco. I do not know enough which Jelco it is. If the 750, it has an effective mass of 13.5. I believe the 550 is only 9.5. Models ‘below’ the 550?

Neither should be too heavy for the 103. In fact, per the calcs I am looking at, either *should* work.

All that said, I think to get better sound, a higher end & better performing cartridge would be my suggestion. And as a Soundsmith owner and fan, of course, that is what I would recommend. But, something like a Hana ML would also be a good choice for a decent price, and I would think, far better than the 103.

Are you chasing the Quads or the Lyra / Triplaner ?

and yes, I have a Lyra, Triplaner and Quads...and a SOTA/FT3/Hana ML. I put them somewhere....

How old are the Soundlab ?

Your friends setup is a lot more money but that is not the critical part it is tweaking your system to work with each other better try a solid state pre for your pass amp even a good used one will blow away a tube pre amp. The impedance mismatch between tube and transistor gear can cause real problems.

Sound lab speakers are FANTASTIC, so I don't think my weakness is the downstream components. Everyone is giving great advices. Ideally I would upgrade both the cartridge and the tonearm. But changing the tone arm on a SOTA TT is a lot more hassle, with no SOTA dealers around me. So, the cartridge upgrade is probably easiest to pull off not to mention the very high price of a top notch tone arm like Triplanar.