Congrats! IMO a nice start to the Spydie addiction. The Para is one of Spyderco's best hard use FFG folders, and the Cento3 with its nice FRN handle, the Palladium silver bug inlay and the 2mm thick blade is a real slicer and much "more" knife than one would think (I made that mistake, too, until I got one!): bigger, sturdier and heavier than pictures will tell.
The Cento4 with Wharncliff blade is disco'd and maybe available as a steal rifht now....
but you don't want to miss out on amazing different designs of Spyderco like the Caly3, the Bradley, the Chokwe, the Stretch(!!!) and so many others, so perhaps you could think about getting one of them instead of a backup for a knife that will last forever anyway without needing replacement
Dennis
EDIT: Did I just recommend nearly all the Taiwan made Spydies? Well, that's how great they are.... but the FRN Stretch is IMHO THE knife every Spyderco enthusiast HAS to own. Japan made, of course.

THE BEST EDC Spydie if you ask me. And SAL's favourite....