The next generation of interferometric gravitational wave detectors will use low-noise single-frequency laser sources at 1064 nm. Fiber amplifiers are a promising design option because of high efficiency, compact design, and superior optical beam properties compared to the current generation of laser sources for gravitational wave detectors. We developed a reliable 200 W single-frequency fiber amplifier architecture to meet the application requirements regarding relative power noise, relative pointing noise, frequency noise, linear polarization, and beam quality. We characterized several of these amplifiers and discuss performance variations resulting from manufacturing tolerances and variations in amplifier architecture. This study serves as a baseline for further power scaling via e.g., coherent beam combining experiments.