I have a 10" REL that I've used with several speakers over the years and it has worked well with both stand mount and floorstanders. I have had the best results with low crossover points, like 60Hz or lower and running the main speakers full range.
My dad has Concertos with a Velodyne DD10 and it's awesome for a compact system.
Some of the newer subs have built in EQ, I would suggest looking at those first. I'm using a Velodyne SMS 1 to EQ my REL and that coupled with a Auralex isolation platform and it delivers awesome low end .
JL and REL are great sounding subs in my experience