Jman-
If you find that you are getting hungry eating in the 2000-2500 range, I think that you may try incorporating some foods with a high water content into your diet. Foods like watermelon, cantalaupe, strawberries, baby carrots, and so forth. With their high water content-they are pretty bulky for the low calories. I cup of sliced strawberries is about 45 calories...a cup of watermelon is about 50 calories. A small sized apple is about 80.
Protein does take a little longer to digest so it is beneficial, as you stated, to eat protein to feel fuller-but it is also important to eat low calorie fruits and veggies to "fill out" the meal or snack with low calories so you feel fuller and more satisfied.
I find that when I stay in my calorie range-if I eat too many high calorie foods-I don't eat as much "food" so I feel hungry. If I eat lean protein and healthy low calorie foods like oatmeal, fruit, etc. I eat the same amount of calories-but have more FOOD in the day. So...maybe you can look at what it is that you are actually eating.
Feel free to pm me if you want to discuss the nuts and bolts of your diet.
Digital Girl-
I agree that as you lose and get to a lower weight that you have to do more-either increase exercise duration or intensity-or lower your calorie intake to progress further. This is why I suggest eating the highest calories that you can get away with and still lose. (Jman-if you are losing a pound a week eating about 2500 a day-DO IT!!!

) When I plateau, I do a few things. I increase my exercise intensity-either by walking faster in the same amount of time, rehearsing (dance troupe) longer, increasing my weights during strength training, walking a longer distance-whatever I can to burn more calories and add muscle. I eat "cleaner" for a while-staying away from junk even if I am staying in my calorie range. If all else fails I will lower my calories a bit-but not drastically-like going from 1600 to 1200. If you drop it too much at a time and then plateau again later-you don't have anywhere to drop it further without being unhealthy.