Anyone using two McIntosh 275's in bridged mono?

I am driving a pair of JM Lab Alto Utopia speakers and am purchasing an MC2300 tube pre from Mac. I am either going to use a pair of MC 501's (500 watt mono transistor) or a pair of MC 275's (75 watt/ch tube stereo--150watt mono). I tried the MC 2102 (100 watt/ch tube stereo) and it seemed to "run out of gas". Has anyone tried a pair of MC 275's bridged to get 150 watts? How was your experience? What were you driving with them and at what volume levels do you usually listen?

Thanks for all responses,
Pepe