when we are gone for the day, we can drop the temp a bit and heat up the house before we get back home.
This would be a PITA with a "programable". Ask me how I know !!
With any of the WIFI thermostats you need at least 5 wires. If you have to rewire it, go with 7 wires. The "Nest" is probably the most expensive out there. There are less expensive alternatives. If you go to Lowes or HD, they have a full display where you can see them side-by-side and consider the features and price. But the wiring will be your issue. Rewiring should be no big deal ... secure the new wire to the end of the old wire (really well) and just pull it through.
