I've been super worried about constant high voltage in my area.. apparently it was explained to me "stepping" the voltage down from intermediate to home levels costs the power suppliers money and if they can leave it a little "higher" like 125 or 127 they save money on their bottom line. They are not supposed to do that. Its like an offense or something if someone calls them on it.. but its not often reported.
But that higher voltage stresses the components in older power supply designs and runs them hot, shortening their lifespan, especially for things like electrolytic capacitors.
APC makes a power conditioner with a mode switch for Mexico and the US, if you deliberately set it for Mexico it ramps the higher voltage down to a more normal range. So misconfiguring a power conditioner may help to protect and extend the life of your equipment.
Ametek makes a very complex Power Surge Protector and Monitor solution called the ESP which is normally used to protect things like Copiers and other heavy equipment, its not MOSFET based and doesn't burn out. You can find them a lot of places, but generally they cost more since it protects more expensive equipment. It does log events when there are power spikes and sags and can be programed explicitly to shutoff the power when certain limits are exceeded. It also has a simple serial port cable which can connect the USB port of a computer to the unit so you can monitor it real time or program it. Its a bit more than what a standard UPS will do for you, but you can use it in conjunction with a good UPS.
UPSes tend to "Catch" voltage surges and sags within a certain interval, but don't really protect from those events.. they really just jump in once they have a chance to detect a surge or sag and make a quick decision.. time enough for damage to occur to some equipment. A true "Online" UPS costs a lot more.. but actually isolates the equipment from the mains all of the time. But it costs a lot more.
Building a firewall against all the things that can occur on the mains feeding your equipment can cost a lot, but can be built up over time.. monitoring the source is a good first start.. its hard to defend against what you can't see. After that starting with low cost UPS and graduating to a more expensive one (after) you've see the monitoring logs of your source probably helps justify the extra cost.
I'm not sure about PureSine versus Ramp design UPSes, except that Switching power supplies definitely do not react well to Ramp designs. The feedback can shorten the life of a good Switching supply in a desktop computer.. if it will even boot. I guess it all depends on how large the Snap Capacitor on the Input of the power supply board for the Tivo.. its going to have to absorb all that Ramp and smooth it out if you don't have a PureSine source. But I could be over thinking it.