I have two 8 speed road bikes with Sora that I would not swap for anything. You can mitigate the "lack" of gears by careful choice of the front and rear gear sizes. One bike has 52/39 front and 26-13 rear, the other 52/42 and 25-12. What is missing from most 8 speed cassettes is a 16 tooth sprocket, as far as my riding preferences go. However, you can realise varied gear intervals, or outright range with appropriate choices. As for extra sprockets, my best bike has 9 speed 105, and I dont feel any overwhelming benefit from the extra gear. Mind you, 5 years ago I was amazed that my 5 speed was so outdated

Ed