For true spot and stalk, if you are going to have a rubber sole on the ground, nothing beats plantation crepe. It does wear fairly quickly compared to carbon rubber and does not have great traction on many surfaces, but it is by far the quietest rubber sole on the market. The cheapest way to get these soles on Cabelas or Clarks "Desert Boots" style shoots, but those do not have the best foot or ankle support for hiking and hunting, especially with any weight on your back. A much better and more expensive option is a pair of Russell Moccasin boots where you can order any sole you want. One advantage of the Russells is that if you don't like the sole or wear it out, you can send you boots back in for resoling. I have some of the Russell PHs and like them. They are designed for mostly dry, non-mountainous conditions with only a light pack if anything on your back. The main draw back of the Russell PHs is their $300 price tag and long wait. The advantages are custom fitting, custom materials, and the ability to get extensive repairs or reconditioning. There are lots of models to choose from for different conditions, and the prices can get lots higher than $300. Also, I don't recommend the Russells for extreme hunting conditions like sheep and goat hunting, but that's not the kind of spot and stalk I think you are talking about.
I have lots of different boots. The hard sole boots are noisy from being hard. Many of the lightweight boot like the Merrills have hollow spaces in the soles that make them amplify sounds like sand or rock abrading on other rock when you walk. The Vibram Light Airbobs are some that you would think would be noisy for that reason, but they aren't because they are made of a softer material. They also give good traction and wear well. I have a pair of Russell PHs with the Light Airbobs for general purpose hunting in drier conditions like Africa because they are a good combination of being fairly quiet while providing good traction and wear resistance. But when I really want to be sneaking up on an animal, the Airbobs make more noise that I would like, so if I think I will be making close stalks I wear the PHs with the plantation crepe soles. Nothing else comes close. If you want to go cheap and get the same level of quietness, go with the Cabelas or Clarks Desert Boots. On dry, fairly level ground where you are not walking for long distances, they work just as well for a fraction of the cost.
The other boots mentioned are good boots, and I have most of them, but they simply do not compare to plantation crepe when stalking game up close. All you have to do is talk to an African PH about boots and you will hear that their #1 complaint is noise. When I wear my crepe sole Russell PHs all they do is ask me what size I wear, hoping I will leave them behind as part of my tip!
Allan