Sota/Koetsu Vermillion---what arm?


I am looking for guidance in the most bang of the buck, tone arm. Compatible with my Sota & Koetsu. I presently have a Sumiko F4, and would like to upgrade. Used ofcourse.
route30
Have you considered a Micro Seiki MA-505? IIRC, it has the same spindle to pivot distance (222mm) but might take a slightly bigger armboard hole (28mm).
If it is any consolation, the Koetsu tonearm was made by Jelco, and I believe I'm correct in saying the Sumiko was, too. If that's the case, you could do a lot worse.
Looks like I am stuck with the Sumiko F4, with the Koetsu for now.Any opinions on how compatible this will be? Any comments or suggestions will be appreciated.
Most bank of the buck is a FR-64s (with intact bearings), that one was also my best match with my Koetsu Rosewood Signature Platinum. From the modern Arms the Graham Phantom was the best choice.