I second Ernest Langdon. I had his Level II action job and a set of Heine Slant Pros put on my P220. His turn around time was about 2 1/2 weeks and the change in the trigger was remarkable to say the least. The double action is about 7.5 lbs and the single is about 3.5lbs and smooth, with a clean break.
Teddy Jacobson also does wonders with the Sig action. I have a P220 and a P226 done by Teddy and they are just as nice as Ernest's, but the pulls are heavier at my request, 10lbs DA and 4lbs SA. EL replaces the trigger with his own smooth faced trigger with with a built-in solid over-travel stop.