I bought a complete number of springs from Elite Firearms to replace all the springs in my mags and they do seem like high quality. I've also bought mag bodies, followers and floorplates from them too that were the same quality usgi.
Alot of people do like the Wolff springs and having used there guide rods in my Beretta's I wouldn't worry about them being anything less and was going to replace my usgi M14 mag springs with them and keep the others as spares. There is a thread though over at the M14forum that I hope turns out with David Tubb's who makes a great chrome silicon op rod and hammer spring set looking into making magazines springs for the M14 out of chrome silicon. If that happens I'll replace all of mine with those and buy spares because from what I've seen from the chrome silicon material it's the best choice out there today and far better than music wire/usgi.