You are very right with this approach. I went the same way , started with a Philips 5.1 @4k in 2006 , upgraded to Edifier DA5000 pro in 2011 @ 12k used till 2016 when I decided to get a nice HT system.
Auditioned Yamaha HtiB and did not quiet like them , tried Polk TL1600 and Vx479 @67k and liked them & really enjoyed them till I tried bookshelves in 2019.
I too enjoy these incremental experiences as I clearly understand what I am getting out of each upgrade. If you go for a satellite + nice subwoofer ( the Polk sub is quite average tbh , satellite speakers are quiet good) you will get a really nice experience .
Viz. A step by step approach. In life also there is no escape from this approach. A baby born today would have to go through crawling, baby steps, walking with support, running, somersaults, kindtergarden, primary school, bicycle, high school, college, first cutting class and going to the beach, first crush, first beer, first love letter(watsapp msg these days), graduation, motorcycle, first job, first appraisal, first salary raise, first promotion, first SIP in mutual funds, first marriage (oops sorry, only marriage is better here), first child, first car, first apartment, first big screen TV, first SUV, first HTIB, first low end home theater and finally the best HT! Mission accomplished and terminated!