I am not so sure - if indeed you do take weekend breaks in Europe anyway, and are prepared for the additional costs of a long stopover as the cost of an additional two weekends away (at least one way each weekend in CE) then it becomes more attractive.

The OP should note that there are some great deals WT+ MFU exMAN to NYC, which would simplify the connections, and also consider www.maxjet.com (WAS, NYC, LAS) and silverjet when that starts up next year.