You can run 3000Mhz modules on the motherboard, but they will just need to be set to 2666. DDR4 modules start at the default JEDEC standard of 2133Mhz. If the modules have the settings programmed into them, they can tell the motherboard to automatically set to 2400 or 2666 if supported by the CPU and motherboard. If the motherboard doesn't automatically set those speeds, you either have to manually set speed, timings and voltage or use one of the XMP settings programmed into the module.Yes I would have too but someone said my mobo wouldn’t support 3000 mhz
I'm currently running two 2x8GB kits rated at 4000Mhz, but I have manually them set to 3000, because of CPU memory controller limitations with Ryzen 2000. The XMP settings exposed to my motherboard are 3866 and 4000, so I can't just set a profile and expect it to work. That is why i was saying that you need to check that your 3000Mhz modules have an XMP setting for 2666 in the bios, before you buy a second identical module. You just happened to buy it before I posted and although it's rated for 2400Mhz, it shouldn't have any issue matching your 3000Mhz module at 2666 assuming they work together at all. The only way to know if they will work together is to try them.