You could also consider a Natural Gas furnace with a AC combination if you want AC. We survive without AC for the week or two when it's needed, but I have friends who love their AC. In hindsight, I probably should have added AC when I replaced my furnace.

Run the math for the more energy efficient equipment. When I ran it before mine was replaced, the break even point for a high efficiency furnace was so far out, it just wasn't worth it. The same thing goes with buying a higher output furnace. In this area, it just doesn't get that cold. The same thing goes for the ondemand type water heaters vs a conventional natural gas model. The initial outlay is a lot compared to what you are saving.

The savings may make sense now, but don't assume it does.