Being an HI and not an HVAC tech, this article sounded reliable to me. I'm interested in the opinions of you that are HVAC techs and you other experts. If you take the profit motive for the installer away are these valid reasons for replacing the part of the system that may be perfectly fine condition? We will assume that the sizing matches up.

What Consumers Don’t Know About Central AC Could Hurt Them

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The only reason some people get lost in thought is because it's unfamiliar territory.
- Paul Fix

Thom, that article is spot on. We always "match" our systems. I NEVER take an indoor unit and couple it with an outdoor unit of a different SEER. Depending on the difference between the SEER it could be like using a 2 ton indoor coil with a 5 ton outdoor unit. The efficiency and life expectancy of the sytem go down and will cost the HO more money in the long run.(energy costs and system repairs)

I personally want the best for my customers so I won't sell them something they don't need. If I cheat my customers word spreads and I no longer have customers. I have been on several "no heat" calls only to find the t-stat isn't in heat or the batteries in the t-stat were in wrong or dead (battery operated t-stat, which I do not recommend!!). I fixed the problem and went to my next call, no charge.

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Stupid should hurt!

I would agree with the article as well.

Mis matching never has a good outcome for anyone.

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Measured Performance more than just a buzzword