Greg,
Like you, I think that the pre-made first aid/emergency kits have stuff in there you don't need and that is just there to boost the item count. The AMK products are a good starting point though if you pick the small to medium sized kits.
What I have done, since I wanted to make more than one kit (pack, car, some for the kids, etc.) was to buy containers for each kit I wanted to make, then I went out and bought bandaids, antibiotic creme, motrin, immodium, zerteck, alchohol prep pads, etc. for the general first aid part and repackaged them in snack or sandwich sized zip lock baggies. I then supplemented it with 4x4's, gauze, tape, etc. for wounds in another baggie. I found a good deal on some compression bandages and some tourniquets to complete the trauma components. I put the desired mix of components in each container and I was done; one for the vehicle, an individual kits for myself and my kids.