Both boards are rock sollid. The extreme 9 has a 12+2 powerphase digi vrm. and a better lan chip. However the Sabertooth is offcourse a rock solid board aswel, with 5 year warrenty.
well the motherboard supports up to 2450mhz OC ram. So you can run ram up to that speed, when overclocking the ram, it supports upto 1600mhz by default. But that is basicly with all boards, you need to set the ram speeds by hand in the bios, But thats easy.
But honnestly what is the reason why you botter about the ram speed? ram speed does not matter at all for gaming. there is no diffrence between 1600mhz or 2400mhz basicly, because the games are using Vram, which is alot faster then your ram. So it basicly does not matter for gaming, lower cache latency is more important then highspeed ram. CL9 ram is the sweet spot. 1600mhz or 1866mhz does not matter much.