ADK, did the insert get installed with an insulated block-off plate in the damper area?
Your next biggest bang for the buck is finding leaks and heat losses and addressing the problem at the source. Sealing leaks is generally pretty cheap. Insulation more expensive but usually worth it. That work will pay off year round. Does NYS or your area have a house energy audit program? If so, that might be a good first step.
I don't think there are any free or low cost energy audits in the area for residential customers. I believe there is one for commercial customers though.
I'm going to go against the general feel of the board and say the Englander 30 isn't all that. It is a box that contains a fire. It does that well. I like the design of the little Century much better.