I don't know if you need to go to SEA, but if you're just talking about a mileage run, I might suggest you look into fares to/from PHX and LAS...

NW is just hammering HP on flights from NYC to PHX... and the short hops out of PHX/LAS on HP are direct cheap because of WN...

NW LGA/PHX $128 r/t
CO/NW PHX/PHL $258 r/t