msmcleod
The main question you have to ask, is when you take your mixes out of your studio and play them elsewhere - i.e. the living room hifi or your car - does it sound more or less the same, or (more importantly) still sound good?
 
If the answer is yes, then ARC2 is probably not a priority.
 
For me, I'd play my mixes on my hifi and there was literally no bass whatsoever. All of my mixes sounded awful. I'd play them back in my studio, and they'd sound fine.
 
ARC2 totally fixed this issue for me.
 
The proof to me was that after setting ARC2 up, my mixes sounded just as bad as they did in the house! So I did the necessary adjustments, and it sounded good in both environments.