I'm guessing you have Lombardy poplars, the tall, skinny jobs? They're not
very long lived anyhow, and are probably close to the end of their lifespan.
Actually, most of the poplars have very short lifespans and usually brittle
wood.

Consider leaving the two remaining ones for a couple of years while you
replant the area with longer lived species. Then when the new trees have
gotten established, take down the poplars.

Depending on where you are in NH and the ground temperature, it might be
possible (and perhaps even advisable) to get the new trees in ASAP,
like within the next week. I'm on the other coast and about that
far north, and I'd still plant out here but that wouldn't be an option
in higher altitudes.

You might also consider some big, fast-growing shrubs for quick color and
form in your front yard, with the plan of taking those out when the new
trees get bigger.