Concord, Ducane, ArmstrongAir, and AirEase are all part of AlliedAir... which is owned by Lennox. They also make MagicPac, however that is a different product entirely.
As BL said, the furnace is from the Lennox plant. The coils come from ADP in Miss, they have microban technology in the pan. The Armstrong and AirEase AC and HP units come from a plant in SC, the Concrod and Ducane AC and HP come from Mexico. I have toured the plant in SC, nice clean and efficient place with a strong dedication to quality; I was impressed (I have been through 4 different plants, this is by FAR the most conscious of QC). You can learn about them here:
www.alliedair.com
I left Ruud and went to AlliedAir (in my area it is Ducane and AirEase). I looked at Goodman/Amana pretty hard, however made my decision based on the supply house... better customer service and generally for me the place which handles AlliedAir seemed the better place for me to trade.
The ONLY issues I have had with these units have been TXV... The coils all use external TXV's, and I have had 2 bad ones this year. They are not hard to change, they are bolt on. Just takes some time to pump down and replace. An elbow section of CO tube with the fitting for the equalizer line from the TXV is included with the TXV kit, so installation of the TXV is not much work. Beyond bad TXV's (I am not aware of any co which has not had TXV issues), I think AlliedAir products are every bit as good as any other co. They have 16 and 18 SEER 2 stage (not dual compressor), they have VS drive furnaces and AH's, they have 90+ furnaces, and they have a 96% MOD furnace (uses standard T-stat).
One thing I like is: When they have their annual Spring product update meeting for the Dealers (us contractors), they ASK us how we want the equipment made... and some of our suggestions are actually incorporated into the products.
They ARE clamshell HXE's... however the HXE's are only 12,500 BTU's each (more per furnace), so they do not run as hot. IMO this could contribute to less HXE failures.
Warranty service has been good, and the product is easy to install.
Given the poor rep Goodman/Amana has in my area... I think I made a good choice.