Psychoanalytically this is the range we hear as the loudest right? So a small cut in this range will sound more extreme then the same -db at other frequencies? And if you want something at the front of the mix you want these mids to be accentuated right?
I thought the optimum hearing range was somewhere around 2000-4000?
Maybe its just my ears being weird then 
But about ducking things and boosting things within the 500-1000 range I think it is generally considered the “muddy” area and as such sounds messy, so ducking it has a considerable affect on the track in making it sound cleaner, cleaner tends to sound louder too. Duck it by about -0.5db on a master channel and it has a considerable affect for example.
You shouldnt really be boosting things in that area if there is no point (obviously :P) for example hats…
To make something louder what you want to be doing instead is ducking everything else that goes within that sounds frequency range… The result will be more space within that frequency range resulting in that sound being clearer and therefore percieved louder/more prominent.
That area is better boosted for things like those dirty distorted basslines or female vocals, etc. etc.
EDIT: BTW its a lot harder said than done. I have known these rules for a while and still cant apply it properly (laziness more so than inability but meh…).