My $.02 on the DGR setup:
One of the most FANTASTIC reliability mods you can do for the money. I bought mine used, with the metal bushing, for $15 shipped - and it was still in exquisite condition. They are very well engineered and machined. I'm using the Wolff 18# spring (stock spring equivalent) right now because my XD is my duty weapon, and no modifications are allowed without written authorization from our weapons instructor. I have a 22# spring I'm itching to throw in there, but I'm waiting until I put a few more rounds through my XD with the 18-pounder before I tweak it any more.
I don't have any experiance with the other products you mentioned, but as with anything, mods depend on what you want to do with the gun.
Sig Sauer Traditional TacOps 1911
Springfield XD-S 45
More knives than I can count