When you have speakers that don't fit, the ONLY option you have, is to either cut the OEM "screen" out, and put an adpater on the door itself, then a guard over it. If you don't want to do this (I personally wouldn't, it just looks tacky), I suggest you get shallow speakers. IDK if the NX's rear ports will accept those speakers you have, but if they do, you may want to put them back there (unless you already have aftermarkets installed back there).
Just use the factory 4x6 brackets,with a little trimming on them and the back of the doorpanel for clearance you should get them in.
I have done this on 2 cars(nx) in the past,and once I put 6.5 components in no prob.
If you don't have the brackets,I have a spare set I will sell you
I cut Some pvc at an angle and used it with an 6.5" Infinity separates for years. Just take a dremel and remove as much of the plastic behind the grill as you can. The new ED 6500's were too big for that, So I removed the map pocket, as described above and mounted the Speaker on the outside of the door panel behind the map pocket grill. So you have several options.
FWIW I put a pair of Infinity 6022i's (6.5 inchers) in the doors of my daughter's 1993 NX2000 yesterday. I pulled the OEM 4"x6" mount out, screwed in a 1" thick speaker ring and attached the speakers to the mounting ring.
The Infinity's are spec'd at 2.75" mounting depth, but they fit - it was tight - but they fit and sound good.