I personally like the 500NE better than the 470NE, but that is a personal thing. By "Jump to" if you mean "up" then the 500NE is a good place to start, but most here would consider the 500NE not much better than the 470NE. As far as resale goes the 470NE is far easier to sell quickly than a 500NE double rifle.

There is nothing wrong with jumping "DOWN" however. I would personally rather have a 450NE double rifle that either the 470NE 0r the 500NE. It is far more versatile, and the bullet selection is not only cheaper but numerous in choices. With proper placement, the 450NE will do the same job as the other two, but is not only easier on your shoulder, and lighter to carry mile after mile, but is far easier to learn to shoot well. Besides the 450NE is the ruler that all other double rifle cartridges are measured by. That round started it all with smokeless powder.

I've owned a couple of 577NE doubles, and I simply do not like them. They are heavy, by necessity, and are simply not pleasnt to shoot. The 470NE, and 500NE are,I find,about most shooter's limit for recoil, and weight, and IMO, they would be better off with a 450/400NE 3", or one of the .450 bores. It is easy to learn to shoot them, and because of the cost reduction compared to the bigger rounds, you get to shoot them far more, and because of that become very proficient with them! In the end, the rifle, chambered for what ever cartridge, one must be able to place bullets where they do the most good. The .400,and .450s give you that edge!

Like Dan said, if the 470NE fits you, and you can shoot it well, then I'd be prone to stay with that!