There are many air conditioning companies to choose from.   It is very important you understand and have faith in the company you choose and the products they install.  If you read only the first paragraph of this page remember;

Today’s consumer prices make your Heating Ventilating and Air Conditioning decision among the top expenditures for your household.  Unfortunately, because we don’t pay attention to the HVAC system until it fails, we undervalue what a correctly selected and installed system can give back in energy efficiency, comfort and dollars in our bank account.  Over 80% of homes have issues that installing an up to date air conditioner will not fix.  These new home air conditioners, once installed, operate at only 60% efficiency due to the overlooked issues within the structure.  This can translate to a (hypothetical) summer utility bill of $200 per month and it means $60 to $80 per month is being left on the table for 4 to 5 months of the year or more.  If I put $30 per month in a popular investment portfolio it will yield well over $8000 over the life of the air conditioner.  Average corrections to a duct system are half of the investment yield.  This calculation does not include lower maintenance cost, longer lived equipment and most importantly improved comfort, which is extremely difficult to assess value on.

Due to inappropriately selected equipment, poor design and inadequate air flow on existing systems, corrections will actually pay for the improvements in a relatively short time.

If we think about it why utilities pay rebates for selecting new equipment its a simple calculation.  The utility understands it will get rebate funding back as a general rule, in  7 years.   This return is based entirely on technology.  If we follow trends back thirty years, we find if a consumer replaces the environmental system (HVAC) every 12 to 15 years, the technology along will justify another rounds of investment.