Mathew, what's your opinion on speakers?
A lot comes down to taste and interaction with your room, so they should be your primary concerns.
I owned a pair of LS50 Meta and although I could hear strengths in them, they left me cold overall, and I certainly felt they needed to be turned up considerably to sound their best. This was having tried them with amps including the Quad Artera Play+/Stereo pre/power combination - plenty of quality power and current delivery on tap.
Depending on the size of your room I would be inclined to give the B&W 707s2 more opportunity to shine, they're very talented speakers. However, in your position, I would also have thoughts of selling all 3 pairs and buying something along with the new amp, or switching to a powered/active solution.
What kind of sound are you looking for? What are your musical tastes?