Bill
As you can see, my system is pretty unspectacular yet I can run the NGX fairly well.
I use Active Sky 2012 with Flight Environment graphics, Ultimate Terrain X Europe, FS Global Ultimate and MyTraffic Lite. I tend to fly from larger airports, some with payware scenery - mostly UK2000 British airports and a few Aerosoft European hubs (but not Schipol, which is very hard on frames!).
Crucially, I have a set of saved display settings in FSX just for running this particular aircraft - no autogen (but very dense scenery complexity so the airports look good), no cars or ships, airliner only traffic at 20 - 50% and water effects Mid 1.x. I also have an unlimited target frame rate.
With this, I get about 16 to 18 fps in the cockpit, and at least double that outside. The UK2000 airports are best for frames, and with these you can also remove AI traffic completely and just use the static aircraft supplied as part of the scenery. These don't actually look too bad when you're concentrating on flying you're own aircraft.
I think if you're prepared to ditch autogen and AI traffic, and tinker with the other settings, you can get a very smooth experience flying the NGX. It's basically all I fly these days...
Hope that helps you a bit.
Ian