Yeah, doing a whole house ductless would be a tough feat and really expensive. They're not really made to be a primary source of heat. Those little things are badass for converted attic spaces though.
2 stage systems are nice energy savers so the upgrades depend on your up front budget. As far as brands any of the major brands are fine and most of them share manufacturing lines, similar to the car industry. We use Carrier in most of our markets.
OP, I'd be happy to help you out in more detail if you need.
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