Personally, I would go for the pair of F110s. Two subwoofers are far more accurate than one subwoofer because of the manner in which they energize the room. While Missioncooney likes his REL's, I have been very unimpressed with them when I have heard them and frankly think they are overpriced.
You might also want to check out a pair of Rythmik F12G subs while you are looking. They are a very musical, servo controlled 12" subwoofer and run $1350 plus shipping for a pair. Tyler Acoustics uses the Rythmik kit with his own enclosure for his subwoofers.
You might also want to check out a pair of Rythmik F12G subs while you are looking. They are a very musical, servo controlled 12" subwoofer and run $1350 plus shipping for a pair. Tyler Acoustics uses the Rythmik kit with his own enclosure for his subwoofers.