I wasn't using room correction in my RELs.
I actually had an acoustic analysis of my room done, using just my speakers and no subs, and it showed:
"Both speakers show peaks at 38Hz and 49Hz, though the left dominates the combined response. Higher up there's a peak in the right speaker at 91Hz that dominates the combined response."
I've since changed the position of the speakers and though it sounds more musical with better articulation in the bass, I have no idea how it measures.
IMHO, to make sure you end up without some huge peaks in your lower response, I HIGHLY recommend room correction in all frequencies occupied by your next subs. If you are not the adventurous type and don't know how to perform the analysis and correction, then find someone who does and employ them. There are a number of folks here who use JL subs and I know those subs have some kind of EQ in them. Check with them since JL subs are highly regarded. In fact, Steve Williams, "Superintendent" of this website, has a pair for sale.