After getting 6 or 7 estimates, interviewing people, and asking questions that most consumers do not know to ask I selected Hancock Refrigeration. I did so much research to make sure I got exactly what I needed and I couldn't be happier. I am not sure if they do oil furnaces, but I would look at getting a Heat Pump instead of straight AC. Then use your oil as backup when it gets colder. Once you get your load calc done they will get your set point to run as efficient as possible.
Hancock Refrigeration
(301) 475-8298
Toll-free Phone: 1-800-863-1259
PS If your looking for some forums to do research on let me know and I can PM them to you.