I own a 2000 sf home in Denver and would like to upgrade heating/cooling system. I have gotten 5 bids and each one of them has given me very different advice. I welcome suggestions about the best (effective and efficient) way to upgrade my home.

My house was built in 1900 and has a 4 ton, forced air, 80+ efficiency, five year old gas furnace with ductwork to the first floor only. Prior owners "popped the top" to add a second floor about 10 years ago. The second floor is about 900 sf with one large master bedroom, a walk in closet and a bathroom with no attic. Electric baseboard heat was installed in second floor. Heating bills in winter run $300 a month with 100 for gas and 200 for electric. The upstairs tends to be 10-15 degrees warmer than downstairs on warm days (I haven't been there in the summer yet but imagine it will get worse) Running ductwork up to the second floor will be difficult in the best case.

I want to add a/c to the house, mainly to keep the master bedroom cool, remove the electric baseboard, with a moderately short time horizon -- I don't expect to live there more than three years.

Here are the proposed solutions:

1. Install separate Panasonic split a/c unit upstairs with heat pump. Install a/c on existing system downstairs.

2. Install Mr. Slim heat pump unit upstairs. No a/c downstairs.

3. Install 3 ton A/C on existing system. Run 8 inch duct to master bedroom; 4 inch to bathroom. Don't add new return.

4. Install 4 ton A/C on existing system. Run 4 6 inch ducts upstairs and install return upstairs. Ductwork will be very intrusive in downstairs.

5. Install 3 ton A/C on existing system. Run 2 8 inch ducts upstairs, add return.

I am leaning towards option 2 as it is least intrusive and will (I think) meet my needs.

Thanks in advance.