This really depends on what the measurements are exactly. Power, noise, FR, distortion, rise/decay? Do you know the amp's power into YOUR load, or is it a very different load? Are the amp power specs true RMS or some marketing gimmick like PMPO? Is the distortion calculated with just one frequency and at one output level, or across the whole audible spectrum? etc You get the idea. Some equipment can have very limited and selective specs designed to hide the flaws. Then there is the issue of equipment which just does not work well with other equipment due to impedance matching, etc, even if they measure well individually.