[Casey]

Hi Gargamel
Love the name!!
If you adopt a puppy, then everything should be fine no matter what breed it is - at least from the pup's perspective. ALL puppies are submissive to older dogs until they begin to approach adolescence, by which time he will be well used to your spaniels (and poodle) and there should be no problems.
The only thing I would be concerned about is introducing a little puppy to a house full of older dogs - three dogs is a real pack, with pack structure and everything. If the other dogs don't like the puppy, it could be quite hard on him - especially with a high-strung breed like Weimaraners.
You would need to introduce them very slowly over a period of time. If you can find a Weimaraner breeder that's fairly local, it would be good if you could choose your pup at about six weeks of age, and let him or her meet your other dogs (as long as they're all up to date with vaccinations) over the next couple of weeks. then when it's time to take the new puppy home, they will all at least know each other and it won't be quite so overwhelming for poor puppy.