2.7 amps at 120 volts is about 320 watts give or take a few. Divided equally to the Motion 40s puts about 160 watts each. The speakers are 92 db efficient at 1 watt. If you are actually feeding them 160 watts you should be hearing a SPL around 115 db which is really freakin loud. The room size could be a factor or maybe something in the room absorbing sound but at any rate it should still be very loud. Remember too that the ML 40s are 4 ohms nominal so they are a bit harder to drive but well within the capability of the 5000. Check the speaker trim settings on the 975 to see if they are being trimmed excessively and make sure the DRC night mode is off. Did you level equalize them using a SPL meter?