we all know how little they really come into play.
I think you've been missing out as there is quite a lot of sound coming from my QS8s, specially in movies
That's until you hear the VP180
If you want to upgrade, I would suggest first the QS8s. Then M60s if it's mostly for music or sub if it's mostly for movies.
As for the crossover, there is no correct answer, you'll need to play with it and set it at what you like most. People like to start with 80Hz and go from there. On my M80s, I usually have it at 40Hz for music and 60 Hz for movies.