[jeffh]

I suggest you get nothing more than a 2-stage furnace. If your fancy direct drive motor goes kaput along with its module, you'll be looking at replacing a $1600 in parts, plus labour. Not worth it, in my opinion.

As for make or brand to purchase, I'm pretty sure the jury is out on that one. They are all so similar, but I do have a soft spot for Goodman and Armstrong.

The key thing with any new equipment is the quality of the installation. Improvements should be made, where possible, to the old ducting system, to keep airflow and air pressures strong, so you can get the most out of your equipment. Mention having them install a condensate neutralizer, complete with a proper bypass, between your furnace and drain location.

As always, I recommend replacing your hot water tank(to a high efficient model) and furnace at the same time. This should bring cost savings by the install contractor, via a bundle discount, to the possible savings for the need for multiple concrete cores, plus the elimination of a combustion air pot(cold air thing near your furnace). Then, the vent stack can be removed in future home renovations, freeing up some space above grade.

And if you have a mid-efficient furnace, do what you can to keep it going, for as long as you can.