There’s a thread on the Heating and AC forum that’s been running for two years debating the issue of high installation costs. It’s a great read; the link is below. Mini splits have been used throughout the world for decades, but are new in this country and there’s very little competition to bring installation costs down. Most homeowners and many contractors have never heard of them. With increased efficiencies and units that can now heat a space when the outside temperature is as low as -15 degrees, they’re starting to become better known and more available in the northeast and Canada as an alternative to oil heat in locations where natural gas is not available. (This is not a sales pitch, lol; I've become obsessed with the subject.) This year, for the first time, I’ve seen a few local HVAC companies running ads for mini-splits (I live near Albany, NY). Installation of the wall unit is probably easier than the ceiling cassette or ducted style, which is one reason I’ll likely go with a pro. To the OP (sorry to hijack your thread), please let us know what you decide to do. @bstruss -- From what I've read, the Friedrich mini is manufactured by one of the big Japanese companies. Though Mitsubishi, Fujitsu and Daiken are the top tier leaders in the field, there are many lesser known units for much less $. Some of them get great reviews. But I haven't seen any other specifically marketed to DIY homeowners. Let us know what you find out about the Friedrich. Here is a link that might be useful: Why is split ductless so expensive when installed

OK, I went out and took the access panel off my old system and found it's an HS16-651, so it's a 5 ton unit. Also, I went down and pulled the access panel on the furnace and checked things out more thoroughly and my furnace is NOT a variable speed furnace, even though the motor is a variable speed blower motor. It turns out the motor isn't original to the furnace. It's a 92% efficient lennox furnace and 11 years old. And to further clarify, my old system cools adequately on most days, but not on the hottest days when temps are at or above 100ºF here, which occurs on anywhere from 5 to 25 days a year here depending on the year. On other "normal" hot days it cools the house only adequately, but not efficiently or easily. It runs quite a bit to maintain an adequately cool house and the air coming out of the vents isn't all that cold feeling. I think part of this is a venting problem and we only have the minimum amount of return vents that we should have, but I've felt the other part is the A/C itself. That's when it runs all the time, but never gets the house below about 76ºF or so in the coolest part of the 1st floor and about 80ºF in the coolest part of the 2nd floor. Thanks again for all the help and replies.

Many " As a result of a remodel done by a prior owner in the 1990s, the house has a central air and a furnace, but no air conditioning." That statement is in conflict. House has central air but no AC. Start with a load calculation for correct sizing. To your questions. 1. No. I would suggest an 80% eff two stage var speed furnace correctly sized. 2. SEER is all about savings. For LA, I would want 15 SEER minimum, your choice though. 3. 75 Db is relatively quiet. No higher though. You want a condenser that has a compressor sound blanket for noise control. 4. Good ductwork system is all about size, design both supply and return plus insulation qualities. How many returns do you have on each floor? It will be difficult to have consistent temperature from floor to floor with just one system unless you add a zoning control. Of course that would come with a cost. Do you have damper control on the supply trunk lines between the floors? Always suggest a dealer thoroughly inspect ductwork system. 5 CFM speed adjustment is in all furnaces whether single stage or two stage. I recommend a two stage furnace. Of course you will need a true two thermostat for best operation. 6. I always recommend a pleated filter media cabinet for indoor air quality and protection of blower motor and evap coil. IMO

Check out Hitachi and others. They have a remote condenser, and in room evaporators. Great for a retro fit.