If a 1.5 ton cooled and dehumidified well but ran all the time, what in blazes are you doing over doubling the size? You had better be ripping all the ducts and putting over double the duct capacity in too. And increasing the number of supply & return vents.
I can't believe 2500 sq ft in CT needs 3.5 to 4 tons. You'll barely run and have high humidity, even the 2 stage since low isn't much less than high .Then you'll need a whole house dehumidifier.
You likely will never recoup the investment for 16-17 SEER either. Good for the salesman's commission which is likely why Mr. Trane was pushing them. Rheem is good equipment but 4 tons without changing the main duct size???? Wow, you have some real winners up there.
Somebody better find out what you have (if you can post model #s in & out we can tell you, somebody, even you, should do an accurate heat gain, then see what you need. But if you kept comfy with 1.5 ton and only complaint is higher than desired bill, you sure don't need those monsters being quoted. Short cycling and if they reuse that small duct system, you may not see much of a savings.