I think that is a great office system!
Only comment I have is unless you need the money from the m8 for the new system, hold on to it a bit longer and test out your system at home with & w/o m8 at various volume levels.
I think you won't miss much assuming normal office levels w/o sub, but it is a shame not to take advantage of the opportunity to trial ls50 with sub for education/future reference . I believe 100hz is recommended xo frequency, but I know
@PENG has done a very thorough job of dialing his in!