I have 2 Xantrex ProWatt SW 600 inverters, 1 for emergency power for the house (small loads only), and the other does duty providin 110VAC to my computer network during power outages.
The network unit runs all the time as it is the backup power. I use a Xantrex ATS to switch between shorepower and the inverter. Everything works very well.
Now, as to noise, the inverter only gets noisy when it's under serious load. My network forces it to pull roughly 40Amps from the battery bank. This causes the cooling fan to run, and yes, it is noisy. Once the loads are dropped (shorepower has returned) the fan shuts off a few minutes later.
This unit has never faltered, and has been on since it was initially installed and powered up in 2011. You can read about the install process here:
Mike & Bernie's Website, Network Backup PowerCheers!
Mike