I keep thinking and going back and forth that my head is spinning so I might as well ask for some advice here, maybe it will stop.
So far I have a Nikon D90 with which I'm mostly happy. The lenses are Sigma 8-16 DX, Nikkor 16-85 DX VR, Nikkor 70-300 VR, Nikkor 35 1.8G DX, Nikkor 50 1.8D. As a backup or light travel I use the Sony RX-100.
I feel the inexplicable need for a new camera.
Rationally I can explain it as:
a) a need for backup body and some weather sealing D7100
b) a lighter travel kit: micro 4/3rds
c) a full frame D600, less likely D800.
While the lighter kit is still very appealing, the current cameras are not exactly what I want although OMD comes close (would like a better grip, similar to G5, if I add the RRS L-plate is same weight as GH3, slightly better movies, integrated flash) and a new system with the lenses that I want would be around 5k while weighing 60-70% of my current one. If I take the essential lenses it can be just 50% of the weight, but space more than weight is the issue.
The D600 (or D800) is quite nice and I always had a desire for full frame but as my first need would be for a travel in 3 weeks or so, I am looking for something lighter. That and I'm not sure I would be willing to put the money and effort (in carrying them) towards the best lenses for it. I could get it same weight as current though if I just use 24-120 F4, 70-300, 85 1.8G +/- and 35 1.8 or 1.4.
The cheapest by far and the "rational" choice would be to stick with DX. Although I'm not entirely sold on the sensor (I hate potential artifacts) the better focusing, some weather sealing and better resolution and maybe noise do make it compelling.
So if I buy the D7100, what lenses would be a good upgrade to maximize the quality? None of the ones that I have are the greatest but I shoot mostly stopped down and around F8 or so I didn't see many to be significantly better in resolution. Maybe contrast and probably bokeh. While I have my eye on a 85 1.8G the sister 85 3.5G micro makes more sense as I don't have any macro lenses.
Any other suggestions? Sorry about the long and probably confused post.
PS. although cheaper is better money are not the top priority here