Fidelity Research 64s vs Jelco SA-750e

The FR-64s without B-60 base (vta of the fly) is not so good.
I have’t tried the N-60 stabilizer

But 64fx is good as it is, becase the arm base of the 64fx is much better than the arm base of the 64s.

So for the 64s you need the B-60 base which is optional and very expensive.
With 64fx you need nothing, but the right counterweight (heavy counterweight W-250 is optional and very rare!) 

I owned both the Jelco 750D (9-inch) and the FR-64S played with my RSP. The Jelco was tweaked with the old TTW VTA collar which, like the B-60 base, adds even more weight to the arm. The FR-64S was without the B-60 Base. Head shells were Yamamoto HS-4 (Carbon Fiber), HS-6 (Titanium) and Ortofon LH-8000 (Laquered wood).  
In my system, the overall difference was small with the edge going to the FR-64S.  The FR with the LH8000 had the best combo of bass extension, midrange beauty and extension on top. Perhaps the difference would have been even greater with the B-60 base but it was enough that I was happy to sell the Jelco and do not miss it. I think the difference is small enough that you can take your time to find the right FR-64 (condition wise) for your table. 

Though I haven't had a stock 64S base, I'd agree with chakster that the stock 64fx base is really nice and solid. It's also very easy to dial in VTA with this base - not as easy as with a true VTA base, but easy enough unless you like to change VTA between records. 

This is great feedback! Exactly what I had hoped for. Karl_Desch, what a break for me that you have experience with both of these with a  Koetsu. Thanks so much.

I haven't made a move on tonearms yet, and instead changed phono stages from my ear 834P to a Joule OPS-1. I had Rich at Signature Sound upgrade caps to Jupiter Copper/wax and he also improved power supply. My God what a fantastic component! I cannot believe how organic, non-fatiguing and magical it sounds. Everything is a notch better in terms of convince people and instruments in real space. By the way, Rich was so great to work with. Super conscientious, careful and his work is beautiful. A+ for him!

So back to tonearms... Does anyone have an opinion about how much better the FR-64x or 64s might be than the Jelco 850? The 850 would be a drop-in replacement and no worries about weight with my aging Sota. I will either get the 850, or, if the FR arms are significantly better, wait and upgrade the table to a Nova or Cosmos and get an FR arm down the road a bit.

Thanks
Stu