Interesting thread! We have had all sorts of pedigree dogs throughout my lifetime and associated with plenty of other types too.
Be careful with large dominant dogs like Rotties and Dobermans - I once road tested a homeless male Akita and it was a real eye opener to feel his strength. There would be no way I could hold an animal back like that, if he decided to go for it (and I am a fairly strong, tall female).
And it only takes one slip-up to see your dog end up possibly destroyed. It could just kill someone's cat...that's all it takes.
The other thing I thought of, with the Akita, was that I would never be able to lift him into the car, on my own, in a medical emergency....a small thing - but when your dog can't jump into the back of your car for a ride (old age, arthritis etc) - will you be able to lift it in?
Do you want an "interactive" breed? For me, for example, I love and enjoy dogs that are a pleasure to train (intelligent), can retrieve balls n frisbees, are confident but not aggressive, form strong bonds within our family (loyal) and can be trusted almost all of the time...
We have a Staffy (STB) and she is real sooky - neither watch nor guard dog! She is a killer of small creatures though - chooks, rabbits etc - so she cannot be trusted in that respect.
We now have a Schipperke pup - and she is an excellent watch-dog already.
Guard dogs are quite different - they need to be trained to be a "protector" - much like the police train their dogs. They are, in effect, a dangerous weapon.
Dogperson - if you don't think you can handle an Amstaff - then maybe a rotty, doberman and G.shep may be a problem too?