Nice design ^_^
White & Grey
This one is very smooth and modern, will print easily, have you thought about getting some silver on the print itself rather that just shades of grey? it'd make the whole thing shine in a very attractive way and would certainly stand out.
Black & Orange
Nice and retro, but make sure that the shades of orange will print as you have them.
when prinitng, consider a high-gloss black and a matt orange, or maybe the other way round, this would really bring the design out in a very pelaseing manner.
White & Orange
Nice, not much to say about this one, apart from a high-gloss print for the ornage and a matt finish for the card would work well.
with regards to the text on the rear with the contact details, try aligning it to the right, or perhaps justify it so that it is all the same width with equal borders around the bottom and sides, this would make the card look more balanced.