I have a GSP too, and I bought the SportDog Sport Trainer 700m (
https://www.amazon.ca/SportDOG-Brand.../dp/B00EE13Q7K). Good range, water proof, basic functions (nick, constant stimulation, beeper), and works great.
Personally I wouldnt get a GPS collar, as I find that no matter where my dog is, she is trained that when I hold down the vibrate button, she has to come back ASAP. For me this collar does everything, and will work great for upland, waterfowl and general off leash hikes and training etc.