DxOMark just tested the Nikon D3300, and the results are pretty much what one could have guessed them to be. However, there is something important to gather from the results.
The expected part: the D3300 scored almost identical to the D3200, D5300 and D7100. The differences are very minor. Of those four, the D3300 has the highest color depth and high ISO performance, but the lowest dynamic range. Even so, those differences are minor and would never be noticed without close side-by-side comparisons of 100% crops.
The important part: you are paying for features when you opt for the D5300 or D7100. Image quality is the same on the D3300 as those cameras. You should consider what features are important to you so you don't end up paying for features that you don't really need. Can't decide between the D3200 and the D3300? Image quality is nearly identical between the two, so perhaps the price should be your guide.
Are DxOMark scores important? No. Also, be careful not to have G.A.S. (Gear Acquisition Syndrome).