I sell fitness equipment for a living. Here are my suggestions for you.
The treadmills you are looking at are home treadmills. They are higher quality home treadmills. Instead of buying one of those new, I would instead recommend finding a commercial fitness equipment dealer in your area (they don't have stores) and see if you buy a refurbished heavy commercial quality (the kind you see in a gym) instead. You will be getting a much higher quality treadmill for a better price. Check with the company to see what they mean by refurbishing. For some companies, it means giving the treadmill a good cleaning and slapping on a new belt to make it look nice. A good company will strip the unit down to the frame and rebuild it, replacing the worn parts with new OEM parts. Also make sure that the company from whom you buy it has service techs relatively close (like in the same state or within an hour or two if you leave near a border) and don't claim to be part of a "service network". Most companies will give you a 60-90 day warranty, but you can sometimes negotiate a warranty of up to a year if you want.
One of the nice things about the Nordic Trac treadmills is they are iFit compatible. iFit has an app where you can track your runs on your phone. Then, when you run on your treadmill, you can log into iFit from the treadmill screen and it will duplicate your run (automatically adjusting the treadmill for incline) on the treadmill using Google Maps/Earth technology. If that is the route you want to go, I would suggest a deviation on the Nordic Trac (NT). NT is part of ICON Health and Fitness, which also owns iFit as well as Free Motion Fitness. FM has a commercial version of the Nordic Trac called the Incline Trainer. You can usually get a refurbished FM Incline Trainer (make sure it has the iFit compatible touch screen on it) for about $3000-3500 (cheaper than the new NT).
Good luck with your search.