Are you replacing an old system or is this a new installation in a new home, or in an existing home?

Ducts are as important as the equipment hooked to them. That is if you want ducts. Personally, I'd stay away from them in many cases.

I don't have any ac. I have oil baseboard heat

You are not in a big cooling climate then? Do you plan to get a heat pump to lower your heating costs? Can you put your ducts within the existing envelope or do they have to go in the attic or basement, if you have those? The former is much better. In retrofits, you might want to consider mini splits. Look at Sanyo, Toshiba and Mitsubishi web sites if you are not familiar with them.

Where are you located?

I'm on Long Island. I have an attic no basement. Oil baseboard heat. Colonial 2 floors. 1st fl approx 2300 sq ft and 2nd fl 1700 sq ft. house has about 35 windows. I have a new Diblasi oil furnace with a 35 gal hot water heater.

Do you have a crawlspace?

Yes a crawl space. half my windows face east half west. Family of 5. 4 bedrooms 2 baths upstairs. Avg insulation. I like the master suite really cold.