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
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