When I had my stem swapped out, I did it while I had my bike professionally refit to a more aggressive, aero position. What I THOUGHT I needed in a stem (and what a few of my friends recommended) was not what I ended up with. And yes, we did try a number of options. And no, it was not something I could have done myself. I don't know how mechanically-inclined you are, but I'm not a gear head and there was no way I could have done it myself.
The carbon stem and the fitting cost be about $200 (I got a club discount) and I couldn't be happier with the result. No discomfort whatsoever.