This would make a really good story,
Sg-1 discover a stargate factory!
I mean, the ancients must of had some way of masss producing them, for example when they were exploring the pegasus galaxy, they just arrive at a planet, and stick a stargate on it!, and there are alot of planets to stick stargates on!
They might even find DHD's there, and could bring one back to use at the SGC
Another point ive thought of is, if the ancients removed the control crystal to stop the inter-galactic link with earth to stop the wraith from getting there, how did they manage to do that to every single gate in the pegasus galaxy before the wraith took over that planet.
Its seems more likely to me that, they removed them anyway, and kept Atlantis as the only stargate capable of reaching Earth, simply to monitor inter galactic activity. Or maybe even, only the flying cities can use an eighth chevron?!
DIAL THE GATE!