I have Maggie 3.7i's. I have a pair of REL S/510 SHO subs. Last week one of the subs lost power and even though I had one sub working the change was dramatic. The midrange was hard and the upper range was rolled off. I hardly noticed the drop in lower registers.
I had been using a grinder without ear protection and thought I damaged my hearing, it took me a few days to stumble on the loose power cord. Presto magic again.
I did not spend time on the sub placement, one is in the back of the room and one on one side next to the outlets they are plugged into.
Maggie's need good electronics and even then I have found the more power conditioning the better.