Between Career Infinity and Amana AMV 9, which is a better furnace in terms of customer satisfaction. Also between Amana and Career which is a better 14 seer airconditioner?

You won't beat the comfort of a furnace controlled by the Carrier Infinity Control Thermostat although a Carrier Infinity furnace can be controlled by a conventional stat. It just won't be as comfortable.

The stat keeps track of faults and determines when filter changes need to occur. Every day at about 1 pm it turns on the high speed fan for about 5 minutes to check the filter.
Depending on the model of the outdoor unit, it autoconfigures the stat to match theoutdoor unit cooling capability. The indoor unit is automatically configured.

There are a couple of remote access products available as well. Control from any browser, anywhere in the world for a ~$10/mo fee. There is another remote access solution available too. They cal it SAM (System Access Module).

You might investigate dual fuel for your area. You can use a HP with gas backup.

Look into an Electronic air cleaner. I have the Aprilair 5000, but Honeywell has a model that's supposed to be better. The Aprilair 5000 employs a large acordian-like element, about 10" in depth with an electrostatic grid. I'm replacing the element about every 8 months (when the Carrier system complains) at about $30 a filter.

Customer service depends on your dealer. Consumer help for technical problems is useless. Sometimes the dealer doesn't know and only the technician does.