How much are the following guns worth?

I've gone through my big gun collection and I always wondered what these guns were worth.

Lefever Nitro Special 12 Gauge Double Barrell

L.C. Smith Field-Fulton Double Barrell Double trigger Vent Barrell

S&W .32 Lemon-Squeezer

Remington .22 Model 4 Roll Block

What are some good guns to add value to my collection?

Right now my gun collection right now is mostly just Eastern Block Military peices. I love them all, and have lots of fun shooting them, however none of them are terribly valuable. I do have a few slightly more valuable peices such as a Browning Challenger III, a Ruger GP100, and a Ruger P89, and a Remington 870 Express Magnum 12 Gauge. I'd like to add a few more collectable and valuable guns to my collection, but I'd like some suggestions.