I own the D8 and the S9. I don't own the GC .84 or .68, and unlikely given my falling out with Italian Barber . They shave well, can't do a direct comparison with the GC, but the fit and machining (barring the dent on the main plate of my Lupo .72) is generally better on the Razorock than DSC, but the finishing is better on the DSC than RR. I'm also not a fan of the scalloped head which DSC tends to put on all their razors. So, you have to decide between whether you like your razors to look pretty, or shave well. (If you want it to look pretty AND shave well, there's the upper tier eg. Timeless, Wolfman, et al.).
I use a Karve B plate as my daily driver. Lupo 72 comes out on occasion if I want to change it up. But the rest of my razors are in a mug in the back corner of my den, including the DSC D8 and S9.