Helofan, the RR300 is designed to answer the market call for an affordable gas turbine. By taking a 250 and derating it the component specs can be reduced. Much of the development in a turbine is to get the first turbine stage to handle high combustion chamber temps. Less performance means lower temperatures. It will probably end up sitting between Lycoming and A250 for both performance and cost.
Later note:
As an automotive engines man in a former life, i find the whole certification process for aero piston engines slightly laughable. Admitedly i am not intimitely familiar with the process, but having a design freeze is just wrong. Each year automotive engines experiment with improved turbocharging techniques, coatings and materials. Even in derated form, required for aircraft reliability, the performance is becoming excellent. By not allowing this development to benefit aircraft the piston engines are being left behind - way way behind...
