If the equipment has a halfway decent power supply (which the Holo Spring does by all accounts), there should be no such thing as audible noise in the power line. You're probably trying to solve a problem that doesn't exist.
That said, most home UPSs you find won't be much help when it comes to line noise. The cheaper ones will be an offline design, only engaging anything beyond surge protection circuitry when the input voltage actually dips below their cutoff. Better ones will be line-interactive, but this still doesn't imply any filtering. They just use a multi-tap transformer to maintain a target output voltage while the battery is disengaged (or charging, of course). Without additional filtering, this will still transmit noise.
What you'd need is an online UPS, but even here, keep in mind that no equipment actually requires the perfectly clean 60Hz sine wave you're after to function. The UPS's inverter output may very well be more noisy than your unfiltered outlet.