I've been totally satisfied after replacing various Grovers with UC1. Carl lent me a UC2 he was not using, it's even better. You can get these used for $60-100/m, or brand new MSRP is only 200/meter, same price as Grover, and no upgraditis.
SC3 is still obviously "better" whenever I hear it, more detail, more bass, more magic, very emotionally stimulating and technically excellent. But to be honest, it is also more challenging. The gear must be up to it, and you need to be prepared for a detail and dynamics joy ride. In a direct comparison, SC3 wins, but I find that intense audio quality distracts me from the connection to the music in the long term. I keep thinking "OMG that sounds so beautiful," which is fun, but it breaks the momentum of the song. So I've grown accustomed to the UC2 which gives the calm controlled JPS satisfaction with plenty of musical detail but less wizbang.
Since you already had it "in stock" Steve, sounds like an awesome upgrade!