I'm going to purchase either an ST70 or ST120 kit in the near future. I have Monitor Audio Silver RS6 speakers and they are rated for 40-120 watts. The sensitivity is 91db @ 1 watt. Will I have problems with the ST70 trying to drive these speakers? I would prefer to get the ST70 because of cost restraints. As a last resort I will go for the ST120. Any advice is welcome.