Yes, the s in FR-64s is for steel armtube. No matter what you think about better or not, when 2 with/without are available, the FR-64s will go much faster in resale and I think, it sounds much better too.
Standard wire inside was copper, most have copper wire inside. The buyer had the choice to get it with silver wire inside instead (then you have the sticker for it onto the armtube and also onto the Box).
Taste is different, but when there are 2, the one with silver leads inside is much faster in resale and of course, you hear a difference.
When you go the way with cable change, he has a few to choose (also Kondo...), I ordered his seven strand 34 awg pure silver wire. It has a lower capacitance than the Nordost ODIN 2. Or that one in copper.
Ikeda IT-345 is made later but every comparison I - or others - made, the 64s always was the winner. Better in Tone, much better in physical presence ... well, it is the way it is. I think, the 345 is much cheaper made ... and that counts finally.
When you like your existing Arm...all I can say, yes, the refurbish kicked the Arm into a different sonic league. I had problems to imagine before sending it, but after ...phhh, unbelievable.
Before you buy some nonsense, which is nice until the end of day ... when you think, your Arm is your choice, the refurbish is worth it. In every sonic area you get more ... and more. That is my impression from Mr. Mak.
Others offer also something, but I have doubts they will reach that Standard. My decision was for him and not Ikeda (it is not the old Ikeda and no idea what they really do and how long it will last) or other DIY guys.
The chance to hear it in its full glory is possible with the refurbish. I think, it was a sonic earthquake when it came out and after all these years with all owner changes .... you can listen to a lot and you are probably not a Fan of it for whatever reasons...but I can say, MY Arm now beats everything I ever listened to.