From what I understand N1 and N5 are pretty much the same thing as far as sound, except that the N1 might have a little more rom and a few sounds that the N5 doesn’t have. The reason I suggested the N1 is that you can probably grab one very cheap and has a very nice feeling 88 key piano weighted keyboard for your wife to learn piano on. If that’s not what you need, you might as well get a newer better sounding keyboard. I have seen tritons in the $1000 range on ebay and trinities for less, they will be a better buy then an N5.
Of course if money is not an object, get a Kurzweil.
But it’s all about what’s important to you, and how much you have to spend. I do my sequencing on my PC and already had a decent sound module, so what I needed was a decent board I could really play on, the N1 fit the bill for me (it sounds better then my module too, on most patches). If you want to do sequencing on the board or sampling, then that would affect what board you should buy. You might even want to use a software synth and just buy a midi controller.
Actually, the best thing would be to go to guitar center or sam ash when you have some time to kill and play around in their Keyboard room. Each keyboard has a different feel and sound. I might recommend Korg, Yamaha or Roland (and I do) but you might like the Alesis or E-mu. Only you can tell that.
Gunther