Y-cables do stress preamp more because input impedance is half of one amp's. it doesn't matter much with most power amp, but Meridians have pretty low impedance from the start - 32 kOhm.
in my system G68 to one G57 works better than G68 to two G57s.
re XLR to RCA - you call is correct& but be careful, american and european companies may use reverse pins 2 and 3.

I miss my old Meridian setup.