Coherent | Nufern has a long history of high power Yb-doped fiber amplifier and component development. This ranges from amplifiers in the >1.5kW regime up to demonstrations of >3kW output power. In this paper, we discuss our latest advancements in the performance of high power, narrow linewidth, kW-class, monolithic Yb-doped fiber amplifiers, as well as the packaging of our two newest amplifier systems. Our lightest amplifier offers 1.6kW output power at <4.5kg/kW. This is an OEM version which requires external power, but offers a significant (nearly 1.5x) decrease in overall mass compared to our previous generation of amplifiers. Our 2.1kW amplifier is our smallest and highest power amplifier. It contains integrated electronics to offer a complete stand-alone amplifier, requiring only DC voltage input, external cooling, and software control. This has nearly a 2x reduction in volume compared to our previous generation. We discuss the performance and specifications of these two amplifier packages. This includes power scaling with narrow linewidth, as well as a significant and simultaneous reduction in volume and mass compared to our previous generations. We discuss the packaging challenges with these architectures, as well as the diode technologies which have enabled such a reduction in our packaging volume and mass. We also discuss experimental results in the power scaling of these fiber amplifiers.