I hate to be a confusing thorn in your side and sound disagreeable, but I own an ACI Titan (very good low priced sub) in my second system and I have owned (and reviewed for Stereo Times) two REL Stentor 3s in my main system. I now have the JL Audio Fathoms (I have two of the f-112s because my roon is not real large but you can easily get away with one f-112 or f-113) and, IMHO, the JL sub is better than both. There's an f-112 used on A-Gon for about $1,800 - at that price - it's a GREAT buy AFAIK.
Just my $.02 - I hope it helps.