We have an older respironics one (about 5years old). It has a humidifier and is reasonably quiet I guess. DH needs the humidification as it's a full mask. He can now however snore through it so we need a new assessment. We are looking at upgrading to their newer fully automatic model.
When we bought it 5 years ago I paid $2500 for it, but now the fancier model is about $1600 so has come down in price considerably as the demand has increased.
Respironics have been great with customer service but the cost of parts for it (have needed variously a new set of tubing - DH put it in the bottle steamer to clean it and melted it, a new humidifier tank and now the mask band is fraying) is hefty.