Not a fan of adding a crossover as I prefer my music minimally processed.
+1 @carlsbad. I have two REL in each of my two stereo systems, and have tried low level and high level inputs. The high level (speakon) was the way to go for me, blending better (seamlessly) and improving everything. I still run my floor standing speakers full range. And the REL Baseline Blue was the way to go without breaking the bank on sub wires.