To he honest, I haven't heard or read a whole lot about the Gameseekers. They do offer a great warranty/replacement on them, and they seem to have a lot ro offer for the money.
The ProStaff is an excellent scope for the money, especially the 4x32 rimfire, which is suitable for just about any gun, even the hard kickers with 4+" of eye relief, and the 2-7x32 Shotgun scope may just be the best multi-purpose scope for the money around right now. I've had a couple of ProStaff's and never an issue with any of them.
As for the Simmons, are you talking about the old model or the new model? I have one of each, an older 6-18x40 AO and a new Master Series Pro Hunter 3-10x44. I like both of them, but I admit that I think that the older model is more durable. There's something about the newer one, just the feel of the power ring and adjustments, that doesn't feel as solid. The new definitely has better optics/glass/coatings, and the eye relief is longer too. Don't get me wrong, it's still a nice scope, but the price difference between the old model and the new, there's not enough there to justify it IMO.
You might look at the some of the offerings from Swift Optics as well. The Premium line seems to be a good value with a lot of choices.