Replacing HVAC system

I have learned more about HVAC in the past 2 weeks than I ever wanted to know!  The unit we have now is the York High efficiency model (E1HB030S06A) that we had installed around 1990.  We had to call BGE for service in June, and it was low on R-22, so they charged it up - ran fine all summer.  About 2 weeks ago when we had a couple of hot days, it quit on us, so we called BGE & it was low on R-22 again.  The advice from BGE (& everyone else) is that it would be very difficult to find the leak & that it is really too old to patch up.  We have been told that this old York unit was top of its line when we got it, most likely an 8 SEER.  It has given us good service for 23 years, but it is time to replace it.

We have had several estimates.  (Sears, BGE & a couple of independent contractors).  Prices vary wildly, as do opinions of what is the best value in cost, efficiency, reliability, etc.  Each contractor tends to have their favorite brand & tends to disparage the competition.  Customer satisfaction ratings also very wildly.  Thankfully, it is the end of September & not the middle of summer or winter, so I can really do my homework & decide.  This is a major expense. 

Carrier - 2 estimates between 6-7K for 13 SEER base unit, financing available
Rheem estimate around 5.5K for 13 SEER base unit, with extended warantee
Trane estimate around 4.5 K for 13 SEER base unit, offered air scrubber & extended warantee at 5.5K
Frigidaire estimate around 5K for 16 SEER unit

Consumer Reports rates for least repairs as follows:
1. American Standard
2. Bryant
3. Trane
4. Carrier
5. Rheem
6. Lennox
7. Goodman 

Frigidaire did not make the list, but it is a more efficient unit at a decent price, with a contractor we know who is on Angie's List.  

Most of the complaints about Frigidaire on other sites had to do with their warantee, which only covered parts on most models.  Industry standard is to cover parts for 10 years & labor for 1 or 2 years.