The Infinity series is quieter than the Performance series although for most homeowners the difference would be very minor in perception. You do want to understand the compatibility of the high eff Performance condensers with Infinity furnace and Infinity controller and any functionality you might lose. This is a question best directed to the Carrier dealer.

Link below to Carrier AC condensers. There is a comparison area but rather simplified.

IMO

For some reason Carrier has introduced over lap in the Infinity and Performance AC condensers. The Infinity line used to be 2-stage condensers only, and the Performance was single stage only. Now you can get both single and 2-stage condensers in each.

The overlap is part of what's confusing me. I'm getting bids from four different guys and they're all over the map in terms of what they're recommending, but the front-runner is matching the Infinity 80% furnace with the single-stage compressor and an Aprilaire thermostat rather than the Infinity controller. Part of what I'm looking for in a new system is the maximum synergy from components that are "meant for each other."

What is your location? I would recommend getting a 95%+ efficiency furnace and a system that qualifies for the Federal Energy tax credit.

I would suspect of any Carrier dealer that would recommend an Aprilaire thermostat over an Infinity controller. This makes no sense to me.

Infinity controller first choice, second choice Carrier Edge Thermidistat.

There is not a third choice.

IMO

Mike, location is Washington DC suburbs. I'm getting bids for both options: 80% plus 90+% high-efficiency, but the architecture of the house makes the PVC venting highly challenging. Given the time we expect to remain in the house and the price of gas, we're not convinced it's going to be worth it, so the estimators are doing an Option A/Option B thing. Anything will be an improvement because the existing system (21 years old) was grossly oversized and installed poorly.