UPS compatible with Silverstone SFX 450W modular

[svrndmngjr]

I'm planning to build a freenas at home for storage and Plex stuff. I plan to use an i3-6100, 16GB Crucial ECC unbuffered ram. Asrock C236 WSI mobo. Stock HSF. 3x3TB WD Red. In a Node 304 case. (I chose the SFX so there would be more room in the case. I chose the case because I plan to add 3 additional drives if needed.) I read somewhere that some PSUs that have active PFC has compatibility issues with some UPS'. Maybe someone can suggest an UPS compatible with the Silverstone (has APFC).