Fidelity Research 64s vs Jelco SA-750e

You’ve got a nice system of high quality, so I suspect you would hear and appreciate the difference between the two tonearms. Not that there is anything wrong with the Jelco. The Koetsu would also benefit from any added effective mass, since I suspect the FR64S is higher in effective mass than the Jelco. So in that regard, it’s a win-win. Whether all this amounts to $1300 of happiness, only you can decide, and unfortunately you have to take the leap in order to know for yourself. But think of it this way: If you buy an FR64S, you most likely can get all your money back should it disappoint you, which I doubt will be the case. I recommend an aftermarket headshell with the FR64S, not an FR headshell. I use an Ortofon LH9000 (18 grams) with my Koetsu Urushi, and the Urushi never sounded better. My FR64S constantly surprises me with all sorts of cartridges, high and low compliance, but in fairness, I've not heard the Jelco in my own system.

I’t’s hard to beat a 64fx or 64S for Koetsu. I once had an opportunity to buy the Koetsu-branded arm for a good price, but passed because it was a Jelco build, and my FR64fx (mounted on a SOTA Star btw) was so obviously built to a higher quality standard.

Now I have a 64S too, on a different table. And many Koetsu cartridges. If you’re a Koetsu lover - just get an FR. Koetsus sound more alive and dynamic on an FR than with the other arms I have (Graham Phantom Supreme and Clearaudio Universal, the latter being an awful pairing). Any hint of sluggish, syrupy sound, missing treble, and/or soft bass disappears with the FR. You get even more of the "midrange magic" - vocals are shockingly palpable. And the depth of the stage expands, too.

That said - the FR64fx is a heavy arm for the SOTA. They can accommodate up to 2.5 lbs, and the 64fx runs 2.2. The 64S is heavier and may or may not work - you’ll want to check on this first. A SOTA definitely won’t work with a B-60 base; my 64S w/ B-60 weights in at 3 pounds!

The Star III with 64fx and an old Onyx Signature was what made me fall in love with Koetsu.

And yes - you can toss the stock FR head shells. Some are OK, but you can do better. 

You could also look at the Jelco 850 if you can fit a 9" arm on it. Lots better than the 750.