How far I can go with tonearms on my Thorens 124?

I have recently bought and upgraded Thorens 124 tt with silicon motors grommets, new belt, oiling (if that counts for upgrade :), waiting for silicon mushrooms for the base and silicon nitride ball and new gasket and housing. I was very pleased with all small upgrades (rumbling level is one to mention). I have SME 3009 II impr (early one with Shure logo), and ZYX R50 Bloom which I love tremendously, no doubt why Audiogon is full of ZYX discussion, it is sad it did not go for FUJI straight ahead :).

I have a feeling that I could get more from the tt with replacing tonearm (which I think a basic arm by all means). I am biased because TD 124 is 50 y.o. turntable which has its limitations of the age, yet certain charisma to love in it, so advanced tonearm, which I could use later on another TT might not benefit on current one...

Tonearm choices (I am sorry if touching already happened discussions, hence it might tt related), I lined as Schoeder Model TWO, Morch UP-4, Tri-planar, Graham and Hadcock (GH228).

1) What would reasonable level of the arm to buy, yet to use later on other tt (say Orbe)?
2) I am likely to search used ones, which of those would be easiest/most difficult to get (I am not in hurry, but some might take years for search)?

Of all what I read, Schroeder sounds like the best choice, I am just confused with lead time and how that works...

Thanks in advance.