PSU calculators aren't that accurate tbh, I checked that newegg one though and at least it seems sensible, they tend to exaggerate quite a bit. And for an AMD APU build, even if you add a weak card for crossfire later, it's more than enough with a good quality 450W PSU like the Antec VP450 as an example. A 350W would even do but I usually don't recommend those because the 450W units are usually not that much more expensive and it's just easier because people tend to think a 350W PSU can't run anything.