In reply to:

In my experience, this isn't true; the output of my UPS systems is cleaner than what's coming from the wall outlet.


Well, the keyword in my statement earlier was "reasonably priced" -- which meant "el-cheapo" in your term. Of course, there are many UPS'es that generate true, clean sine wave when you look at more expensive and larger ones. But I thought that spending lots of $$$ was not the intention of the first poster.