You stated that you tend to favour/use your 35mm prime most of the time and not your zooms if I'm correct ?
That being the case I would suggest you try shooting with some of your other lenses why not just go out local with the 18-55mm much maligned kit lens?
Once your back home or even while you are out and about you will soon find out what is lacking i.e. I need to go wider because even backed up to a wall I can't get everything into the frame I want?
The same with your tele/zoom I can't get close enough
You have a excellent kit already capable of capturing great images.
Advice i have always given out is don't fill your bag or load yourself down with kit.
Don't purchase that ultra wide or superfast telephoto until you have found yourself in real need of the extra wide or reach. (More than just once)
Working and shooting with you existing kit will help develop your photographic skills far more than just adding kit and weight to your bag and outings.
OK
The time has come and you really find yourself wanting something wider or longer ?
Now are you sill happy with shooting DX ? or do you still want that top spec FX full frame camera?
If its the later look for the best quality lens you can afford that will be future proof for your FX acquisition at a later date.
But be aware a full frame ultra wide 14-24mm 2.8 or the 16-35mm f4 will give you a narrower field of view on your current DX camera body.
So you will not get as wide a view on your camera as you would with a DX 10-20mm lens.
Enjoy what you have right now
Check out your exif data you will soon find out your most used or preferred focal length
A lot of those awesome shots we see are down to post production skills in PS LR software.