Rob.

With the quality of your kit, you deserve a quality subwoofer. If i had the ��'s it'd be
Velodyne HGS-18 or DD-18 with their High Gain Servo feedback systems, will totally (and i mean totally) outperform ANY of the REL subs.
Amazingly LOW distortion, with clean accurate bass is guranteed with the big Velodynes.
REL stadium, Stentor & Strata are nice subwoofers, but they are not in the class of the big Servo subs from Velodyne.
Go and listen to one for yourself.
There's other good stuff out there, but it's difficult to match Velodyne's ultra low distortion figures.

Adzman