The Tonearm of the PD-171 is already very good. I tried several recent Jelcos and SME 309 and M2-9R.
i have just just installed the LTA-710 which is the tonearm delivered with the new PD-191. You also need to order a new baseplate for it,
Produced by SAEC on the basis of the Jelco TS-850S MKii. Much more refined though and much higher quality.
Beautiful tonearm, clearly better then the Jelco 250 derivate that is incorporated on the PD-171.