You don't get the Prestige calling cards without prestigeing AFAIK. Only time I don't prestige is if I'm near level 55 and doublwe weapon XP is being used for specific weapons so I don't lose them. I prestige my weapons twice over if it's something I regularly use. Even then I might do it for infrequently used weapons because I won't have golded them before I prestige them twice anyway.
Annoying that the Ballista is a level 40ish unlock and the XPR is in the 50s and I'm level 49. Might stop at prestige 5 and not bother with lower end scorestreaks, assault shield and some perks and then I'll have the everything I want.