There are a number of variables which have to be considered. First is your own anatomy, ie. your arm length and upper body size; others are top tube length, saddle position, and stem height. One size doesn't fit all. One place to read about handlebar positionin is on the Rivendell site, www.rivbike.com. Grant Peterson of Rivendell opined that 95% of all bicycle handlebars are too low. This is because that Bicycle manufacturers think that everyone wants to be a racer.

I ride bikes with threaded headsets and quill stems and have replaced the original stems with Nitto technomics. This has made all my bikes much more comfortable. Unfortunately because of the yen's rise in value in relation to the dollar, Nitto products are becoming quite pricey. If you have a threadless headset, there are stem extenders, I believe.