I've used a couple of the SmartUPS 1400s for years as UPSes for my ht system. When I got the zt60, I'm fairly sure I was getting buzz coming from the UPS the tv was plugged into when screen was white/bright. This with THX Cinema mode set to default, or possibly even with contrast backed off a bit. I've since had the tv plugged into the wall, and with THX Cinema no buzzing. Recently jacked up the contrast some (with the Sight & Sound settings), and now there's some buzz, but from the tv, not the UPSs (guess I should double check, see next paragraph.)
Funny thing I noticed today that even with the tv plugged into the wall (different wall plug), one of the 1400s went into backup mode (fans running loud) right when I powered up the zt60. Just a bunch of goofiness going on, probably have a pretty good load going on. (The older 1400s do not run their fans 99% of time unless they are in backup mode. (The newer ones have their fans on all of the time, at a low level under normal conditions.). The 700 has no fan, or didn't when I bought the one in the other room, or if it does, it only runs while in backup mode.)
I do think a UPS will protect your tv, and your disc players, and etc. We get a good number of power losses, some lightning hits, etc and I'm sure they've helped keep my system running well without issue for several years, and not needing to have things repaired or anything (knock on wood). Subwoofer may be exception, but not sure if it had anything to do with the UPSes or just my doing dumb things with it (or the UPS) when the subwoofer was plugged into the UPS; may have got a lightning hit nearby on one particular day, but was not home at the time. Also have similar UPSes backing up my computers as well, without issue.
Anyway the whole point of my post is that yes it would be wise to use a UPS with your electronics, but possibly it might buzz with these tvs.