I have to admit I'm a little stunned. Really lovely.
Almost hate to ask, but it's a problem I ran into very late in the creation process and it caused me a lot of problems in revision - have you tried a CMYK conversion on any of the cards, especially the ones with blues and purples?
Some of the best color values simply don't translate well for standard printing, and better to know at the beginning so you can find ways to work around the problem.