hello i have a 2400 sq ft house in lake worth fla i want to keep the inside temp at 75 around the clock... for ever I'm getting crushed by..... 600.00 $ electric bills........... the 4 ton central ac unit i have is a 9 seer and 14 years old from what i under stand the may tag 24.5 seer 4 ton will make the most cold air for the least amount of cash it comes with 12 year warrantee parts and labor from what i understand please is this the best choice please advise