I will likely join the Kirara 3.0 KR server when it finally starts. Without all the mods that make BR easier, it should be enough to be called hard. KiraraHC is even more harder, but unstable, incomplete and currently not really good maintained.
The only other GT alternative i know of would be InfiTech2 modpack. That is in terms of dificulty beween BR and Kirara.
Cool - I dont think I can wait for Kirara to get rdy, it seems like it will take a while, from what I can read in the thread.. I think I'll join this new one New server based on gregtech 5 unofficial - read inside