Brent - That's a vote of confidence, purchasing one.
I have investigated the details of my existing UPS and they are the APC "stepped approximate sine wave". I am still a little concerned that the Eaton might be completely square not approximate and this might be an issue.
Chris - I'm not interested in the DIY approach although have considered the benefits of it as you mention - big battery, cheap. I want an off the shelf solution which will PnP with my PC to integrate with automation easily.
Matthew - Thanks for your input and clarifying those options. I think in this case the expense of "Online" is not warranted consdiering my old ones aren't "Online" and haven't caused significant problems.