When I did the hub/bearings in my Slo-Noma, the only ones that were worth a sh*t were the AC Delco ones. At the time, I worked for a dealership chain, so it wasn't too bad cost-wise. I don't know who makes them for GM. I had tried a couple of aftermarket ones with horrible luck (one failed after 6000 miles, another had a sensor wire fall right out, one failed after 2500 miles).
I did the fronts on my Tahoe last fall and used Timken units that I purchased through Rock Auto for a song and they have been excellent. Probably put 8000 miles on them so far.