If you are going RCA to XLR because you like the 2 components, then many people would say reterminate your RCA cable on one end...in order to get rid of the adaptor.
As for SE vs Balanced, yes many people feel there is inherent superiority of Balanced over SE technology...however, as with many things in life...it comes down to execution. A well executed SE will still sound better than a poorly executed balanced.