Regarding the inevitable potshots at Chris King as "the" benchmark in headsets... yeah, you can get years of good service from value-priced headsets. I have myself, there's nothing wrong with that. But if you think anyone else is quite like Chris King, then name another headset manufacturer that will make you a custom headset with
ovalized cup flanges, to fit your own measurements, in order to save your irreplaceable ______ frame that's suffered an ovalized headtube.
*crickets*
All rightie then. Having sold lots of Kings in my time, and lots of other stuff too, I won't be casting aspersions on people who decide to budget for a King when they're wallowing in $300-$500 cranksets, carbon forks/stems/bars/derailleurs/bottle cages/seatposts. If you're in the Shimano 105 bracket, however, get something like this:
Dia-Compe AL-series. Lightweight, forgiving of imperfect frame alignment, cheap and easily serviced. And they don't scrape & drag like I've seen Ritcheys do with their plastic upper overcup. Do watch for that upper seal if it decides to herniate out the edge of the cup during assembly, however.