amplifier power consumption

I would be hesitant to use even the 540W ups, without knowing the exact power requirements of your particular amp.

Here is a Cambridge integrated amp rated 75W/channel and spec'd for a maximum power consumption of 600W.

Here is a Creek integrated amp rated at 80W/channel and spec'd for 340W consumption at full power.

So the numbers can vary widely.

Also, I would want to derate the ups capability by a factor of 2 or more (meaning its rating should be twice the expected worst case requirement) to allow margin and to minimize the possibility of affecting dynamics.

Keep in mind, too, that some ups's, especially the inexpensive ones, put out quasi-square waves instead of sine waves. You would want to be sure to get one that puts out true sine waves.

Re the wattmeter that Riley linked to, I would question whether or not it will capture and display very brief peaks in power demand, which is what is important for your purposes.

Regards,
-- Al

Strangely, a very good service technician whom i know suggested using even the CHEAPEST one by a company called APC (the unit that puts out 200w).

That is probably this model, at $49.99.

I believe that when ac power is present all it does is to pass the incoming ac to the devices that are plugged into it, with some degree of surge suppression applied to the ac. One of the documents indicates a total current capability for all of its outlets of 8 amps, when ac is present.

When ac power drops out, or drops to too low a level, the battery backup kicks in after a delay of a few milliseconds. That provides a stepped approximation to a sine wave, which will keep a 200W load powered for about a minute.

So for several reasons (lack of true sine wave in backup mode; lack of power regeneration; completely inadequate power rating in backup mode; and noise filtering which is probably either ineffective or not provided at all) you don't want to let that get anywhere near your audio system. :)

APC's much more expensive products that are intended for audio and video systems, which I understand to be generally highly regarded, are linked to here. And here (on the lower half of the page) are some comments by Kal Rubinson on their model S15.

Regards,
-- Al

It sounds to me like what you need is not a ups per se, but a power regenerator.

As was said earlier, some higher-end ups's will provide that function, by converting the incoming ac to dc, and then converting the dc to a clean 60Hz sine wave.

Something like the PS Audio Power Plant Premier will also do that, without providing the battery backup function. But a cheapo ups will not do that, as has been said, and also creates a risk of damaging your equipment if the ac drops out.

Also, I'm wondering if the buzzing might be due to a ground-loop issue, or to rfi pickup that is specific to your new location. Are you using the same interconnect cables as at your former location? If they are unbalanced (rca) cables, and if they are either significantly longer than the ones you had been using, or if they are a different make or model, that might have increased the likelihood of ground loop issues.

And if there are any nearby dimmer switches, try turning them off as they can introduce distortion on the power lines as well as rfi.

Regards,
-- Al