Damn...I just saw this thread and wish I saw it before you got your lens...(which one did you get by the way?, as I read through the posting as fast as I could so I could reply...)
I shoot the D7100 and so far really like it (I can't afford to go full frame yet as with Nikon it also means upgrading all your lenses so there is no crop). I picked up a Sigma 17-70 F2.8-4 and it shoots really well. It is fast enough and wide enough for what I shoot (landscape, wildlife, product ad shots). I also have a Nikon F1.8 50mm (mostly used for product shots) and the Tamron 70-200 F2.8 which is absoluty awesome for sports shots (my kids baseball) as well as wildlife. I got the lens that does not have the vibration reduction (you can get it for around $800 vs the $1200+ VR model) as I tend to shoot really fast with it (for baseball I rarely shoot anything under 1/2000 sec) so the VR is not needed.
Don't forget you can shoot in RAW and maybe shoot with less ISO for less noise and then tinker with the images in post processing...though all of that takes a lot of time but if your getting paid for your photos (even if its in trade for things like getting into venues for free, concert tickets, etc) then you want a quality product. I often shoot products for fishing companies and get stuff in trade...if you can show details or give the consumer what they want then you will get more work.
Lasty, though I mention processing the photos...as you know, you must first have a good photo to process. I think you will like the D7100 as you use it more (as there really isn't much difference than the D7200 other than built in wifi and a slightly faster processor to write the images...but you shouldn't try and shoot fast in low light anyway without a full frame camera, otherwise you will just end up with a headache).
Grade
PS. So far no problems with me with the off brand lenses...and as far as the super zoom's go (18-300) everything I read about them is that they are no better than a kit lens for image quality...it's just too much to make a sharp image and I know of at least one that broke...that is a lot of movement in a lens each time you make an adjustment.