How many "layers" of surge protection is considered useful?
Before you even start on surge protection, look at your service entrance ground and consider adding to it if it's inadequate by current standards (it may well have been adequate by code when it was built, and still be underbuilt by current standards.) 

For instance, if there's a single ground rod, you might consider adding 1, 2 or even 3 more spaced 8-10 feet apart. An effective ground is the backbone on which anything else you do to deal with surges rests - if it's not good, nothing else will work very well.

The answer I linked in the comment explains pretty much what I do, which is a somewhat layered approach. I guess I can link it again here. What does a surge protector do that a breaker doesn&#39;t?

The version of "whole house" protection I use is not a "plugs into the panel like a set of breakers" thing, so you could run a second set in a (preferably steel) junction box closer to the end-use point if you wanted to. I think they fit inside a 6x6x4 box.