i love your signature line, although i would substitute something else for the chocolate, like maybe another martini.
you have a common problem, i'm guessing this is a townhouse.
by installing dampers you will force more air to the desired level, in cooling upstairs, heating down.
this will help somewhat but can, and probably will reduce the efficiency of the system.
if you start the solution now with the builder, he may have to keep the warranty going until the 5-6 degree temp. difference is achieved. (but probably not, and you wont know that until the hottest or coldest days of the year)
zoning will require alot more expense to him, it WILL be his last resort.
sorry to hear about the goodwin.
good luck