If the AK40s are THE cap for you, I would buy a second set of those. I did this when my 4015s got dinged at Melkweg. They are my absolute favorites, so I bought another pair. I haven't gotten around to sending the dinged pair in for repair yet, but I will do so in the near future. Then, I will always have a pair of 4015s even if disaster strikes.
If you want to experiment with different cards, looking for something you prefer to the Neumanns, go for it, but spend some time listening to recordings out there to see which mics you like before you buy.
Personally, I think trying some other polar patterns would be of interest. The wide-cards and the hypers that jbell mentioned would be good options; staying within a manufacturer's "system" makes it easier too.