A question for ACI Titan LE2 Sub owners ?

With any subwoofer the placement for best bass loading (most even response) may not coincide with the placement for best imaging from your monitor speakers, especially in a small room. Additionally the monitor speakers may not be at an optimum height. Other than this it should work OK. (I own a REL sub, not ACI).

Why do you wish to have two subs ? Could you get by with one and free up some space?

I think that it would be best in your small room to get some decent stands for your monitors and to use a single Titan II LE. I own an ACI Titan II LE, and it works very well in my ~13.5'x~18' living room.

It is best, of course, to place a subwoofer in an acoustically optimum position. However, due to room layout and aesthetic constraints, I can not place the subwoofer in an optimal position in my living room. Instead, it is about 3' to the front and to the right of my Vandersteen 1C's, yet the ACI Titan II LE still does a virtual disappearing act, seamlessly integrating into the Vandys' soundstage. A large REL should function with similar success (but for *much* more money), but few other subwoofers I've heard would be up to the challenge.

Incidentally, the helpful folks at ACI have a newer, somewhat smaller subwoofer out that they call the Force. I haven't heard it, but the Force is reputed to sound and function very much like a less powerful Titan II. It is still probably too large to allow its more optimal placement within my living room, but it is another option to consider.

I have been using ACI Sub one's with Spica monitors on top of them for 10 years. The sub one was the model before the Titan and is basically the same sub without the built in amplifier. Originally I tried to isolate the Spicas from the subs with audioquest big feet but I eventually used blu tak to mate them to the subs. They look like one speaker manufacture to be a tower.
I am sure I lose some imaging and sound stage by having the Spicas on top of the subs. I also know that having the speakers out in the room optimizes the Spica's but not the bass. In general, I am quite pleased with the sound. The Spica TC-60's are wonderful monitors. The ACI in my set up is not thundering but is very musical. It fills in the lower octave for the Spica's. This system is 2 channel music only.

Good luck