Though some will argue the point, it seems most here are in agreement that at a certain point (arbitrarily, lets say 1K, new, retail) any changes in SQ due to electronics are going to be so minimal that it would require the famed Golden Ears to hear said possible difference in a true DBT.
For your purposes, stepping up to a unit with better room correction, and perhaps a better feature set for your usage is the only real reason to upgrade, and any such upgrade should be planned on hopefully lasting you... say 5 yrs. (Arbitrary, again, but...)...
People that love B&W speakers seem to really love them regardless of the flaws. I'm in agreement that if you want to upgrade something meaningful, you need to get away from the 600 Series speakers. There are many other speakers out there that can outperform the B&W600 series. Several B&W aficionados have written here that they don't even consider the 700 series to be worth the cost.
It is your system and your Ducats... your ears, too.
A step up in AVR would be nice for certain. Better speakers, though...