Niel,
Haven't heard the Paradign subs. so cant't comment on their sound or how they'd fare with the Haydns.
For a nice, quick speaker like the Haydn, I should think that a REL (owned by the same parent corp) would do quite nicely. I've got 3 RELs and 2 Velodynes in various set-ups, and both mate well with a variety of speakers be they single or multi-drivers and high or low sensitivity. My preference would be for the REL, as I believe it is quicker and tighter.
Cheers,
Garry