Snoobler handled the warning regarding 20% discharge. Very good way to kill an expensive AGM.
For the regulated 12V output I use a trash-picked
Belkin UPS to power my sensitive router and modem. Output is 3A. Everything else in my office (fan, lights, USB ports) I connect direct to the battery as they are unaffected by the swing in voltage. Easy to find used and cheap units on eBay.