I have a 1700 sq ft home. It is heated with radiators (water not steam). The current boiler is older (home is about 70 years old), but is in pretty good condition. I would like to add air conditioning for the whole house. What is the best and mose economical system for my home?

Window A/C is cheapest. Basement install will require duct to be run and cost more. Attic install Spacepack will cost the most but they do work nice. Just make sure you get the best installer. The equiptment name is not as important as the company putting it in.