I think the protein isolates, like the soy protein in Kashi Go Lean, get absorbed faster than a whole-soy food or a whole-protein food (like eggs, meat, etc.) and so one still gets hungry.
You're right about the peanut butter, Ready2Shed, it does have a lot of fat. So one has to be aware of that, just like the carbs with beans.
I like tuna as a snack with crackers. I add salsa to the tuna, the hotter the better, and salsa is very low cal. Caramba! Es muy delicioso!
Jay