jk: Questions like that are always difficult to answer, 'cause one man's overkill can be another man's barely good enough. Hence I'd rather put it like this: In the automobile realm I'd compare it to a well motorised VW Golf. Or maybe better to a decently, but not yet really well motorised Golf, as the needle of the original cartridge wasn't that great - but with a higher quality needle for the original cart or a different cart with higher quality needle you could easily turn it into a well motorised Golf. So, in case you'd actually already be happy with the turntable equivalent of a decently motorised Up or Polo, the -QX300 would already be more than ok and quite possibly all you'd ever need, whereas if you couldn't be bothered with anything below a well motorised Audi A6 or even a Porsche 911, you wouldn't really be adequately served with the -QX300 yet.
Greetings from Munich!
Manfred / lini