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