If you have your heart set on new speakers, the new B&W 703's have delivered a death blow to the current N804's. For $500 less they sound better in the midrange and they kill the 804's on the top end.
I suspect that your XLO cables might be the culprit. You should try some other brands of speaker cables first and then interconnects. Try to stay with one brand of cable. Let them break-in for a week or two before passing final judgement. Are you bi-wiring the speakers. If not, try a shotgun bi-wire speaker cable.
You didn't mention a sub. Try listening with a subwoofer if you aren't now.
The other brands of speakers that you mention are all good companies. But keep in mind that B&W spends more on R&D each year than all three of those brands added together sell in total sales.
You might want to wait as the new Nautilus line is due out at the end of the year and I am sure that they will sound better. And no, I don't own any, sell any, or work for B&W.