I have had a D80, D300 and currently have a D7000 that my wife is learning to use. The D7000 is decent in ok light. Over the years in talking to local photogs who had full frame cameras (especially D700s) I got the itch to go full frame. I got a used D700 and it is fantastic. Much better in low light than the D7000. The D750 came out and I thought there was no way I'd get one as the emphasis seemed to be going to using video and I couldn't see the point. Fast forward a couple of years and the desire to have even better low light performance and I took months to decide between a dx D500 and an fx D750. I found a really good deal on a D750/Nikon battery grip/24-120f4 combo. I jumped on that and am so glad I did. The low light performance of the D750 I consider magical. The noise/grain is so fine and is so amenable to slight tweaks from noise software. All this to say... if you can afford to go full frame/fx, do it.