Is a pure sine wave UPS the best power treatment ?

Nope, anything is possible. Best line of action is dedicated lines first. Mathematical theory flies out the window when high-end audio walks through the door. Its funny and sad at the same time. You may have 1000 technical papers showing you one thing, vs. simpleton concoctions selling like hot cakes. Knowledge is power I say.

There certainly isn't harm from using a pure/clean sinewave, the PS Audio Powerplants generate an essentially pure sine wave, but as Aerosans points out high end audio is full of "interesting" theorys. Many of them seem like nonsense but many folks think they work. You are the ultimate judge if it works in your system. With respect to your suggestion for a 3000 watt power supply, that would require a 240 VAC line to generate that much power and account for the inefficiency of regenerating the power. Sure sounds like a good idea but anything powered by a 240 VAC source is pretty unusual in high end audio.

Thanks for the replies thusfar. I live in Australia where our voltage is 230 Volts.. I guess I am trying to work out how a audiophile product that just "conditions" incoming power can be superior to a device that generate its own power , supposedly a "pure sine wave". Of course, the audiophile power treatment is significantly higher in cost to the "online" UPS available out there, hence my question.
Thanks