The money you save and spend on ammo will be shot up within a few trips out shooting. You'll be stuck knowing you could have had a better gun for just a little more money for a long time.
I like the 870 best, but I'd not argue that you probably get more for your money with the Benelli. It comes with sling attachment studs, 3 choke tubes vs only one on the 870 Express and is better finished. I just am too used to the 870 and shoot them better.
If buying extra barrels is in your future it is hard to beat a Remington 870 or Mossberg 500 though. Not an economical option with the Nova.