A sub to go with kef ls 50 speakers

I just bought a used REL Q108 MK II (can't find out why or what was improved over the MK 1, whatever that was) to stick in my window for augmenting the also sometimes window placed (used when I'm hanging out on my deck and the windows are evenly spaced so this arrangement works…I run a different power amp than my indoor mains as I have extra outputs on my preamp) KEF Q10s (had these for years and used them for near field recording as well as main speakers from time to time). The KEFs go down to around 60hz so this little sub matches fine when the driver is pointed out the window (uses the entire house wall as a baffle it seems…sounds really good for outdoors). I plan to use this little sub in my main system when the deck is snowbound, and after testing this I think it's a good match, although not really needed (the Q150 I already use provides more than enough mojo for my hifi room)…I run these subs at right around or slightly higher than what appears to be the drop off point of the main speakers…not the -3db point noted by the manufacturer, but where I hear the bass receding when using a test CD on the mains as I think a -3db spec is sort of useless in real world applications.

Dual SVS SB2000 gloss black.

Thanks,i better try one just to know.