An APC for five devices?

Well, that depends on how long you want it to be able to hold up the voltage and the acceptable form factor.  A 750VA one would likely be enough power, but a 1500 would hold up twice as long, at less than twice the price.  Of course, the 1500 would be bigger, too, likely having two batteries instead of one.

I don't have a specific APC to suggest, though the BR1500G looks good on paper and has 5 battery backed up outlets and even an option for an extended battery pack.  I use a Cyberpower CP1500AVRLCD, which is a similar size and capacity; and it is just about as tall as the ProBE.  It does have only 4 backed up outlets, though.  With batteries around two years old, it is currently estimating it will hold up my 3 ProBE/Pro6 NASes for 9 minutes.  A 1500 is pretty much the biggest you will find that plugs into a standard (NEMA-15) outlet.  If you look at something bigger, check what plug it uses.

Of course, the cream of the crop is typically Eaton, and the 5S1500LCD looks good.  Three year warranty includes the batteries (which rarely last me 3 years due to Florida thunderstorms and resulting short power outages).  I have a couple of 5P1500's for equipment that is sensitive to waveform and/or power factor, but those are overkill for what you need.  I got a steal on them on eBay (enough to make me wonder if they were, indead, stolen; but they came up clean when I registered them).

Whatever you choose, make sure it uses a common battery.  Most of the 1500VA ones use a UB1270/80/90 or similar (often with an adaper in between two, but that's movable), and those are available pretty cheap on eBay.  It was hard for me to find info on the batteries in that Eaton, but they do seem to be the standard UB12xx with an adapter.  My 5P1500's use those, though 3 batteries instead of 2.