My house is about 90 years old, a ~1500 sq foot three bedroom colonial. I'm in Northern NJ, and it's getting pretty hot outside. I currently have not enough window units to keep the whole house cool, and I'm thinking it's time to do something.

I've had three AC people in to make their sales pitch. what they have offered (and all of the pretty similar in price is:

a)Split system to just do the first floor (18000 BTU). Outside unit in back yard under the window that now has the big AC, inside unit on living room wall. A couple of fans as needed. ~$3500 (minus $500 state rebate)

b) Same as A, but with a second inside unit in the ONE bedroom (30,000 BTU). ~$5500 (no rebate)

d) Same as C but with a third inside unit to hit a second bedroom (40,000 BTU). $8000

d) Central system (3.5 ton). Outside unit in same place, inside unit in attic, ductwork in 3 upstairs closets, vent in EVERY room first & second floor, return in upstairs hall. ~$7500. 1 year parts & labor, 10 years parts warranty.

I'm at a loss as to which is the right thing to do. Assuming I can afford any of these (I can), what would be the relative advantages/disadvantages of each? How about the relative cost of operation?

Thanks - I want to get this done ASAP, because my other option is to move to Antarctica.