I had a Stratos w/cap upgrade (also currently run Tempest/JD-100 in conjunction w/modified Polk SDA-1Cs), and recently upgraded to a pair of Odyssey Extreme Monos. IMHO - the Extremes had plenty of power to run your Ushers.
The reason I upgraded to the Extremes is that w/the Polks I was getting some midrange congestion on hard rock, as well as the tweeter protection devices were coming into play at louder listening levels. Since the upgrade to Extreme Monos, I have absolutely no issues. The Extreme Monos are not fully burned in yet, but the difference in their power/finesse/detail, when compared to the Stratos w/cap upgrade, is significant - in my system with my components.
The reason I upgraded to the Extremes is that w/the Polks I was getting some midrange congestion on hard rock, as well as the tweeter protection devices were coming into play at louder listening levels. Since the upgrade to Extreme Monos, I have absolutely no issues. The Extreme Monos are not fully burned in yet, but the difference in their power/finesse/detail, when compared to the Stratos w/cap upgrade, is significant - in my system with my components.