If you are going to upgrade, get the Biss-C at €129, not Sincos at €120 (and out of stock.)
I upgraded my Small Mige 10,000ppr encoder with a Biss-C. Is it better? Yes. Is it €129 better? Maybe not. It was an improvement, but I wasn't blown away. However, I'm very happy with my Small Mige/Biss-C.
I upgraded from a 10k encoder to the SinCos and it was a pretty small bump in FFB quality. I've heard that the difference between the SinCos and BissC is even less noticeable so, I'm not convinced it's worth the money. But, if money's not an issue for you, then at least you know you have the best encoder in your system.
I really like the SimuCube but, I'm disappointed in their reluctance to provide more FFB options, such as telemetry-based effects. Ultimately, I'd like a more robust motor (servo) option for the AccuForce system combined with SimCommander but, I'm very curious to see what Fanatec brings to the table with their advanced tuning options too.