Differing info on furnace and AC brand-19 year old home. Please help!

Hi everyone,

I don't know much about HVAC so I am confused by the different information I received from contractors.

House info:
Built in 2001
4000 sq feet
2 AC units for 1st and 2nd floor (3 and 4 ton)
3rd unit for guest room that is above garage
Currently have Lennox
Live in coastal southern CA

2nd floor AC was blowing hot air, tech came out and tried to solder hole that he found. It is a temporary fix and he says its a matter of time before it goes down again.

Looking to replace the 3 ton which has the hole.

Should I replace the 4 ton at the same time? or wait until I have problems? How much longer can I get out of the 4 ton?

Will leave the guest room unit for the time being.

I had 5 companies come take a look and give me estimates.

2 says I won't need to replace the furnace, the other 3 says I do. That is about a $8,000 difference! :eek2::gah:Can someone explain the reasons why??

I've been quoted Day and Night, Rheem, York, Goodman, and Lennox.
Which is reliable?

I'm leaning towards the contractor that recommended Rheem: RA1448AJ1NA $4300 and RA1436AJ1NA $3800. Thoughts?

Thank you!

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