FWIW, I had an emperor 400 for about 5 or 6 years (also a pair of emperor 280's, one of which is still in use). When it died recently, I replaced it with a canister filter, and am thrilled with the quiet. Any HOB filter is going to be noisy, and the emperors make a little more because of the bio-wheel spray.
You also have to be sure and keep the spray bar cleaned out with a pipe brush, because if the holes clog, the wheel stops turning.
Also, the media is expensive. A 4-pack of filters will run you around $20 or so. They can be rinsed and reused a few times if you wish to do that, but they do wear out after a couple times.
That said, the emperors are reliable, and the bio-wheel does a great job of providing a great bacteria media, even if your tanks are crowded. I've never had a problem with an Emperor filter restarting on it's own after a water change, and you can get parts pretty much anywhere.
For a HOB, I like my emperors, but I think I've become a convert to canisters, with the quiet, the ease of cleaning, and the reusable media - espensive up-front costs, but it will save money in the long run.