Just received a quote for a 80% efficiency carrier heater, which includes a air conditioner unit with a XR13 blower for $5,100.
Is this a good price? The air unit is a 14 seer and the installer stated that the XR13 blower will upgrade the air unit to a 16 seer. Is this possible?

80% is minimum you can install. Can't help you without knowing the BTU rating of the heater and the tonnage of the AC.

I would suggest getting some more quotes for 90+ eff furnaces. You won't see a huge savings with a couple seer on a/c, but will see a pretty significant savings on a 95% furnace vs an 80%.