I've replaced my two Alen 375's with two BreathSmart machines. I have found that the filters in the BreathSmart last longer and are much quieter when running at the #2 speed settings versus the #3 speed setting of the 375's. They also do a better job of refreshing the air because of the extra volume of are that is filtered. I have a large home so I was happy that Alen came out with the larger volume air purifiers. I also own a Blueair 503 that I use at home. I'm a fanatic when it comes to breathing air clean. I have had ongoing respiratory issues since I was a kid, but when I am home, I know I can breath easy...