I personally don't really stick to just one Seedbank or specific breeder myself. I shop around. When I want GPS gear usually 90% of the time it comes from GPS website. Especially the auctions and sales and when I have Golden Nuggets built up.
But say Oregon Green Seeds has a pack of GPS for cheaper than what GPS is listing theirs for, I will grab it there. Plus I have found a few places that offer a lot of GPS gear that has been unlisted and discontinued for a while. Such as the Polar Bear crosses, Sky Pilot etc...
I even still order from overseas from time to time especially if I don't need my seeds quickly on a time frame. You can find tons of breeders and banks that offer beans you cannot get in the US. There are great deals with other seed companies and breeders just like there is with GPS out there. You just gotta use Google as your friendly search party. But I will say GPS is in my top 3. Might make it to number one again once my problem is addressed and taken care of that I am currently having with GPS at the moment.