Have you first considered the power cost in your Country in comparision to most countries?
If the power is cheaper per KWh than most parts of the world, then buying the gtx1660 wouldn't be a bad idea. You would only think of the RX5500XT if the power costs were very high.
Yes I'm running on solar setup with 2400 watt solar panel and on a good sunny day my charge controller always display 1700watt available for use, I don't use grid that much, probably just for few hours but most times I mine on solar energy