I've just had to send back my Q150E for the 2nd time in a month due to the 'humming' problems this model developed. I thought the problems would go away with the new back-plate but this was not the case. Anyway, I have now had a refund and am once more looking for a subwoofer, I liked the REL Q150E very much so I was wondering how the Q100E and the Q50 compared and if anyone had noticed this 'humming' on these models aswell. My budget is around £500 so if there are any other makes worth looking at I would be interested in everyone's recommendations. Thanx! mustang.