When you say self install, does that mean you are going to hire an HVAC technician to do the installation, or are you going to buy all the equipment needed to do the installation yourself?

Trane/American is probably the best when it comes to heat pumps. Carrier/Bryant is also very good, but their heat pumps don't have on demand defrost. In your climate it is probably not a big factor.

You need to do a load calculation to determine the size. I would expect the cooling load to be in the 2.5 - 3 ton range. You are in humid area so you don't want to over size the condenser. You probably have duct work problems. Inspect all the duct carefully for leaks. Replace them if they have no insulation or are in poor condition.

Thanks for your answer.
We like to buy all the equipment we need and than install it ourselves.
What is with the on demand defrost?
Since we cool our home down to an adequate level, outside right now 90úF, inside 72úF, with the two small window units and only one door closed we were thinking a central unit with 2 tons would be enough ?? We did the load calculation for 1000 sqft.
We have 1 duct in every bedroom (3), 1 in the master
bath, 4 in the kitchen/eating/living area, all 8" and in good condition, no holes and all good insulated.
What would it be to disconnect the master bath duct (it isn't really needed, it stays very cool there without a/c) and going instead with a 10" duct into the bedroom, or cutting another outlet in the ceiling and set the bath 8" duct as a second one to the bedroom ?
Thanks for answering.

On demand defrost is a feature where the heat pump goes into a defrost cycle only when needed. The alternative is a timed defrost which occurs at fixed times regardless whether the defrost is needed or not. Demand defrost will save energy.

A 2 ton unit may be enough. The size is a function of insulation, the number of windows, and direction the house faces.

It may get hot in the bathroom if there is no vent. You will have to be the judge on that. Moving the duct to the master bedroom may be OK. It would all depend how the duck work is organized.

I wouldn't be inclined to exceed 1.5 tons based upon what you describe (1000 SqFt and adequate cooling with 2 window units). If your house is reasonably well insulated and sealed, that should be more than enough. As Mike says, you don't want to oversize a cooling unit is a humid climate.

As far as brands are concerned, they're all pretty much the same. An inexpensive Goodman system that is installed properly will outperform an expensive Trane system (or Carrier, or whatever) that is poorly installed.

We just installed a 2 ton 16 seer, (basic system. fan speed adjustable, but not variable) split system in our 860 sf house. The house has insulation above the ceilings, but not in walls. The windows are old awning windows, that don't seal great.
Only 1 small s facing window.
We are very comfortable at 77 degrees, and 50 - 55% humidity.
Before putting it in, we had a 16,000 btu thru wall unit, along with fans. With the LR (where wall unit was) at 76 degrees, the bedroom was 80 degrees. With a fan, it was bearable.
Last year, in Aug, the elec bill was $159. This year at a very comfortable temp in the whole house, the bill was $108. !!!
The lack of noise was a big improvement.

Our install was with all new ducts. Be sure your ducts are in good shape and of correct sizes. Having to close some vents to get MBR cool soaund like different duct sizes are needed. If doing over, I would insist that the installer put in ducts that are larger than desired, but with a damper on each branch. That way I could balance the system perfectly. The AC guys who gave quotes, said it wasn't needed. (more work for them) BS!
I would have liked the ducts sized so I could close 1 room off and open the other dampers, and still have proper cfm flow.
Good luck.