If you get aftermarket mags for your pistol, make sure they function with your gun properly, not all 1911 mags are made alike. If you can test one in a store thats even better.
I found a good price deal for extra mags for my Dan Wesson 1911.... bought 3-4 and went home. Started shooting and the slide kept closing after the last shell... instead of locking open. Upon closer inspection the mags were made a tiny bit different and lacked a certain edge to trigger the catch.
I took them back and bought 3 of the Kimber Pro mags in SS to match my gun and they worked flawlessly in my gun.