Looking at the specs they are about the same at 8 ohm, Hafler 50 watts channel, Alesis 45 watts channel. For some reason at 4 ohms the hafler only gives 55 watts but the Alesis gets 75 watts? If your monitors are 8 Ohm you will find them about the same.
I use an old Hafler (can't remember the model) which is about 75 watts per channel at 8 ohm and it cranks.