They should already have a DHD from Antarctica. They never explained what happened to that device after they recovered the gate itself. Additionally in Atlantis they salvaged unused gates to build a space bridge. But what did they do with those DHDs?
Come to think about it, since they managed to go salvage gates for this gate bridge, why continue paying rent to the Russians for the gate that they have. If it were up to me, they could just give the thing back and get another one. It made sense at the time they started renting the gate because they did not have any ships, but later the Russians wanted to take their gate back and the SGC was forced to hand over one of their ships to buy the Russians out of the contract.