The general rule-of-thumb for matching inputs to outputs is found by multiplying the output impedance by 15. A ratio of 15:1 or higher is usually acceptable.
In your case, 300 X 15 = 4,500 (or 4.5K) = minimum load impedance = 15:1.
Insert the powered speaker's input impedance (44,000/300), and you get a ratio of 146:1. That's a factor of 146, much higher than 15, and probably acceptable.
This is a general quesstimation for doing things. Look for optimal impedance matching in the equipments' manuals.