But if you can't afford a custom build then the next best thing is to have your own bike fitted to your individual optimum riding position.
A few months ago I went along for a session at a London bike shop where they used a well known bike-fitting company's technicians. The session lasted over an hour and cost a little over a hundred pounds.
The technician spotted a few problems with my set up on the bike; my cycling shoes were too loose and their cleats weren't aligned correctly, the saddle was too small and too low, and the bars were too wide and tilted forward too much, making me reach too far thus putting a strain on my back.
I was then fitted for special shoe inserts that were heat moulded to my feet, a new set of bars were fitted, and a new Fizik saddle replaced my more basic one. I left the shop feeling more comfortable on the bike but a little lighter in the pocket. After a couple of rides I was happy that I could ride for longer before the dreaded back pain kicked in, I felt like I was pedalling more efficiently, and the saddle was probably a little more comfortable than my old one.
I was a bit surprised, however, when I looked at the old bars that had come off my bike and realised they had been exactly the same size and shape as the new ones that had been fitted. Still, overall I was pleased enough, and was happy to recommend the service to a friend who had shoulder problems which his physio felt were exacerbated by road cycling.
So if you're getting fitted for your own bike, be careful. If they recommend new bars and stem, or a new saddle, don't feel you have to go along with it. If you do, then think of shopping around before you buy theirs at full price. And if they suggest buying one of the bikes they sell, ask what the exact differences are between yours and the ones they're recommending.