This paper reports the design and performance of state-of-the-art GaN MMICs and a fully packaged Ka-band SSPA. Incorporating harmonic tuning, the MMICs produce power levels up to 10 W CW with efficiencies in the high thirties (42% peak) at frequencies of 30 to 34 GHz. These results represent the highest combination of CW power and efficiency at these frequencies. A 4-way combiner-SSPA, operating over 31 to 34 GHz, was assembled with these MMICs. Biased at 24 V, this SSPA produced an output power of greater than 20 W CW with an associated PAE of greater than 30% across the band. Biased for maximum power at 28 V, it achieved an output power of 32 W CW at 32.5 GHz with an associated PAE of 30%. This is the highest reported efficiency at this frequency for a packaged amplifier with greater than 30 W CW output power.