Part of the answer to this is what you feel is 'not too expensive'. I mean you can go to Panera, and it isn't horrible, and is very cheap. But if you want a nice restaurant, there are many in the area that are several notches above that.
As I said in my other post, I heartily endorse Labriola. But having lived in the area for many years, I can recommend a few other places that may or may not work for you.
Redstone: A few minutes down the road from Oakbrook mall, but a really nice place. It is a chain, but a quality one.
D.O.C. Wine Bar: Very nice atmosphere, nice food. Things like Ahi tuna sliders, Flatbreads, Cheese plates.
J. Alexanders: Similar style to Redstone. Quality, slightly upscale food, nice atmosphere. Next to Oak Brook Mall.
Except for Labriola, none of these places are really GNRs, but they are all pleasant with above quality food. You would have a good time at any of them.