the 70 watts per channel and 210 watt sub is the peak power, they will easily (and most often do) work with less watts per channel. For example if I have two 100w speakers and power them with an amp that has 160w per channel, I'm not sending all 160w to them at once. Depending on my volume set, I'm sending a fraction of the 160w. As I increase the volume the more watts I send. So unless I set my volume to the max, I really wont blow my speakers. The reverse will also work, same speakers driven by an amp with 25w per channel. I'll just have to turn the volume up to get the same level of sound.
In your system the amp is in the subwoofer so you will have no issues driving the speakers and the sub plugs into an AC outlet.
one more thing guys.............i seem to be using a 650watt smps...........and it seems to work fine with the 600watt UPS..........but i doubt it would work when playing games like crysis................because thats the time the Graphics card(4870x2) draws maximum power i guess.
First of all, why do you want to power your speakers from the UPS?
Main purpose of a UPS is to give you time to save everything you are working on when there is a power failure. Plugging more electronics into a UPS will just decrease the amount of time you have before the UPS goes dead.
A 4870X2 needs about 20 - 22 amps (240 - 260 watts). Figure 120 watts max for an OC'd CPU. 40 watts for 4 GB of RAM, 25 watts for a motherboard, and 100 watts for 3 hard drives and an optical. Equals about 500 watts. At 80% efficiency, you'd be pulling a little over 600 watts from the wall.
Even if you were at full load the instant you lost power, I think you'd be OK. I wouldn't waste time saving my files though.