Told today that need to replace my 22 year old, Lennox H 519651U-22 AC unit for about $4000. Does this sound reasonable, and is there a better unit than a Lennox at the same price or cheaper. I aggree the coil is shot and it won't hold refrigerant at this age and needs replacing. I just want to make sure to put in the best unit for the money. I am in my 60's so this most likely will be the last unit I need.