Unless your body is unusually shaped, i.e. particularly long/short torso or limbs you should be able to pick the right size by doing the measuring as described in that Surly post. Then yeah, you can change the stem for shorter or longer, or different angle, move the seat forward or backwards a bit, etc. Some minute changes like this are usually to be expected anyway.

Also pay attention to how aggressive the geometry is, for most people a good starting position is when the grips are at the same height as the saddle. The lower the grips, the more aggressive the position that allows for more powerful pedal strokes and better aerodynamics. However, not everyone feels comfortable bending over that low, or even needs it.