We have a 2900 sq ft older two-story home with one ancient furnace that needs replaced along with the a/c. The upstairs (two lg BRs, 1 sm Br, 1 lg bath, plus a landing) has no cold air return. The upstairs is very cold in winter. The downstairs has 3 cold air returns that were laid out in a straight line on one end of the house (one in hall, a downstairs BR, the LR) spaced out 8 to 15 ft apart. The opposite side of the home is cold most of the time. What troubles me is that we have had four "estimates" for a new furnace and none of them addressed running more cold air returns or replacing the existing old ones. Just exchanging an old furnace for a new does not seem to me to be sufficient. What do I look for in an estimate from the HVAC professional that will instill confidence?