No it's not. There is a lot of "marketing" hype about "pure" sinewave output UPS. Don't fall for it! That's all it is, marketing hype.
Any 1/2 way decent AC/DC power supply can handle the "stepped sinewave" or "stepped approximation" waveform just fine. They have for the last 25 years with no problems so there is no reason to believe the much more reliable and robust power supplies of today can't either. They are much more capable at handling power line anomalies than PSUs of yesteryear.
And that's not just computer PSUs, but the power supplies for our modems, routers, switches, monitors and more. The only time you really
need a "pure" sinewave output UPS is when used to support highly "sensitive" health monitoring and life support equipment as found in hospital intensive care units.
All computer and networking devices use DC voltages. It is actually easier to make a clean DC voltage converted from a stepped approximation sinewave than it is from a pure (round tops) sinewave because less filtering is required.
Do not forget that 99% of the time, our UPS is not "on-line". That is, it is not acting as a battery backup, except during a total power outage. It is just "in-line" acting as a sophisticated "automatic voltage regulator" (AVR). It is really for the AVR that we need a "good" UPS. Backup power during a full power outage is just the icing on the cake. But even then, power supplies do just fine with stepped approximation outputs.
BTW, a surge and spike protector is little more than a fancy and expensive extension cord as they do absolutely nothing for abnormal low voltage events like dips (opposite of spikes) and sags (opposite of surges), or long duration sags (brownouts) - any of which can cause your electronics to suddenly stop, resulting in possible corruption. And for "extreme" surges and spikes, a surge and spike protector simply kills power (if working properly) to your components. That's hardly good for your computer, drives, or data.
The only reason pure sinewave UPSs have gotten a lot of attention lately is because the prices have FINALLY come down so they are within reach. That and aggressive marketing from makers of such UPS.
Since they have come way down in price in recent years, they have become competitive. So if you find one and the price is right, go for it. I don't have anything against them. Just don't believe you need it, or that it is better for your connected devices.
FTR, I live in
Tornado Alley where we frequently have severe weather. Total power outages are not everyday, but they are not rare either - especially in my 100 year old neighborhood where the utilities are not buried. I have a "good" UPS with AVR on all my computers in the house, and my home theater audio equipment and big screen TV. I also have one on my garage door opener and even one in the bedroom for the alarm clock and electric blanket!
None are pure sinewave and I have no plans or intentions of replacing any just because they are not pure sinewave.
Me too but a lot of that could be simply because Corsairs are so popular. No doubt, for many people, ASUS' Antisurge feature works fine (or at least, does not cause problems). But for many, problems go away when that feature is disabled.
I note surge protection on the motherboard is not unique to ASUS.
Gigabyte for example, uses anti-surge ICs as do other makers. The difference is Gigabyte and the others don't have extra code that interjects itself into the system. Typically, when one maker comes up with a feature that is successful, other makers soon follow suite. The ASUS Antisurge feature has been around for several years now and yet none of the other makers, that I am aware of, have found it necessary to include such monitoring software. They just depend on their hardware to suppress any surges and move on. And it works. That seems good enough for me too.
. Also have power on after AC loss disabled, have experienced couple time power outages in my home, not switching on after a power outage automatically.
