The model number quoted to me for the 91 BTU unit was a G61VMPV-36C-091. Right now, I manually zone my house with dampers and it works fine. I'll probably continue to do that with additional dampers for the new registers for the basement.
The theory behind moving to a 110K unit (for free) was that the furnace will run in the first stage most of the time, delivering and maintaining more consistent temperature at lower btu's while giving extra airflow capacity with the bigger drive motor with the 5 ton blower wherein the airflow delivery can be adjusted accordingly.
Does that make sense?