Advice please for switch from Leica to Nikon

I'm a long time Leica user and have used the M9 since 2009. I shoot family stuff, street and weddings (professionally - maybe 6 a year). I'm 46 and have been in love with photography since I was 15.

Leica, for me, is about two things: using a rangefinder and the wonderful lenses. However, recently I have missed a handful of what could have been wonderful shots. Well I've not missed them, I've missed focus; only just, but enough to turn them from fantastic to frustrating.

I primarily shoot with 50mm f/1.4 and 90mm f/4 lenses, wide open with the camera either on fully manual or Aperture Priority.

Anyway, I'm starting to understand the true limitations of the M9 - me! I don't want to miss any more chances if I can help it.

I've handled a D3 a few years ago and despite being heavy it felt comfortable. I like the high ISO quality and the dual card slots are very appealing.

Based on what I've said, please can you offer-up any recommendations for a possible system change, especially with regard to quality glass. I'm not overly fussed about zooms.

Thanks,

Steve