The Stereomour circuit originates from the original Paramour amplifiers, which used the Triad C-7X choke as a plate choke and the Speco T-7010 matching transformers as an output transformer. The T-7010 had multiple taps on the primary, and the most sensible choice for operation with the 2A3 was the 4K tap. Consequently, the operating point in the Stereomour runs higher plate to cathode voltage at less current to better match the 4K load. When the Speco transformer was discontinued, we kept the operating point and dramatically improved the iron quality with our own parts.
This is a long winded way of saying that the Stereomour operating point isn't correct for a 2.5K load, but you could certainly drop a little extra voltage in the power supply and run a little extra current, then use your output transformers in that configuration. The one sticky issue will be the performance of our plate choke running 60mA vs. 50mA, PJ would have to weigh in on that one and you may end up having to settle for 55mA or some other middle ground. (You could also just ignore this and try the 2.5K transformer in the stock circuit, there's no harm in doing that)
