Jim,
Go to Train Town. They have prewar/postwar and a backroom for modern stuff. It's unassuming from the outside. I didn't have high hopes when I first pulled into the parking lot of a frowning strip mall. However, on the inside, it's a tight squeeze because they're packed with inventory. I can't speak to pre & postwar pricing since I'm not knowledgable about them. Modern stuff is quite reasonable and mostly LNIB.
Switch Stand- it pains me to say it but you could probably skip. The guy who runs it, Roscoe, is widely known in these parts for being a top-tech. He's not such a great retailer. He's not a mean guy but he's not terribly warm and inviting either. I will say there is some inventory there though so you can look at trains... in silence.
K-10 - I have not been because I'm told it's mostly HO. They are supposed to have a monster layout though so that might be entertaining.
Rodney's - I heard a few grumblings at the local Lionel club that this guy is a jerk. I went in there and he was really nice. He's an east coast guy so he might be a little bit surly for midwesterners. It's almost exclusively used stuff. His pricing was all over the place. I saw a few things that were reasonable. But I also saw an engine I just bought NIB for $300 that (and thought I overpaid) he had marked $500 well used and no box. Anyway, worth a fly by AND next door to the old Frisco viaduct that's marked "Frisco Lines" as you pass underneath (now BNSF).
Schaefer's - this place is less than a mile from my house. It's a general hobby shop but a good one. They do handle O (all Lionel). They have a glass case full of new stuff that is all MSRP + tax so you can skip that. It's a low percentage play but they have a case in the front corner of the store where they sell prewar and postwar. If that's what you're into, you could strike gold there.
Electric Train Outlet - Like Bigtruckpete said: good store, lots of inventory, almost exclusively Lionel. When I was in there over the holidays, the owner was grumbling to one of his buddies the same thing: "I'm too old for this s___. The store is for sale." Blah, blah. So apparently he's been saying that for a while. Good store though.
Haven't been to the other two.
In any case, don't miss Train Town. And the Museum of Transportation is essentially a railroad musem. It's not far from Train Town. My avatar is a picture of my daughters standing in front of a UP Big Boy at the museum.