Clockspeed matters fuck all these days, as evidenced by Wii U's 1.2GHz CPU being around 1/3 as fast as the 3.2GHz PS3 and 360 CPUs yet clearly being more than 1/3 as powerful, and actually surpassing them in some respects.
Factors like cache, IPC, pipeline length, number of cores, etc make a big difference.
Xbone's CPU will do just fine at 1.9GHz








