DIY, all DC is often the way to go if you are trying to run for a long period of time. UPSs are really typically designed to run just long enough ride out brown-outs or to shut everything down safely in a total blackout. Some even shut down if they don't sense a heavy enough load (i.e., designed to assume servers have shut down, and so preserves the battery -I banged my head against that for so long!).

I have everything on a consumer-grade APC now, and I have it set up to give me about 3 minutes of server, + another half hour of basic networking. I do have some marine deep cycles and an inverter, so I could set up the networking to run longer if cell towers were down and I needed it. But I'd likely use the energy for other things.