I have 2 404's and a 305. Never had a problem with them and got them all used, so they've been around the block a few times but they work perfectly and nearly silently. 405 is functionally the same as the old 404, so you can be sure it's a good filter. Some people may have gotten a lemon so they don't like them but search the boards for opinions, it's a good filter. $100 is a great price for a new 405. I say go for it.