Somewhere I got to a webpage that recommended your site, so here I am.
I have no professional certifications, accreditations or employment. Long ago I was a HVAC tech and know repair. I have no installation experience. I have re-hab'd existing residential and small commercial units and air handlers.
Not so long ago, I got an estimate for a refit hvac in a 800sqft house from a retailers everyone would know if I said. The ac is 2.5 ton and the natural gas furnace was 80Kbtu. The estimate was only verbal and I had 3 options. The $ options. Variable fan speeds, to two speed fan to single speed fan. Variable flame to fixed output flame and so forth.
I have a few ideas and since I pay, I figure it should count.
I like split-mini's. They are so quiet and have a heat pump option. I'd need several and the cost is up to $ pretty fast. Many in Asia, and I liked them. Few in the US though. I like the zone idea so the office can stay cool without cooling the whole home.
Hi-V in an idea. Old houses seem to like this. Needs mufflers to be quiet and really nice air distribution in the room. Add a heat element, natural gas flame or HW boiler and the cost is somewhat over $.
Too much for an intro? Hope I'm on-topic enuf.