Anyone use a sub with Reference 3A DaCapo i

No , I have not . I am not a fan of sub integration .

But...
Have you tried rolling the input tubes ?
How far away is your listening position ?
Are you firing the speakers down the long or short walls ?
I have these same speakers and integrated and can get bass
that I can feel , if it is in the music . I am not familiar with your source's sound though .

Admittedly I am in a nearfield situation in a small room but you really can't exspect a small standmount to fill a large room like that .

Good luck .

Hi, I used a TBI Magellan VI with mine and they were a perfect match. There is a TBI magellan VIII on audiogon which is larger than the one I used but should be a good match also. I don't know the seller just saw them come up. These are some of the fastest subs I've heard and blend well with just about any speaker.

thanks for the replies....I haven't tried tube rolling, any that you would suggest? My listening position is from 6 to 7'away. The speakers are firing down the long walls, however there are more room problems. There is an alcove where the front windows are located just behind the speakers. There is also an area to the side that opens out a bit so the room is not a perfect rectangle (at all). I'm also investigating the possibility of getting higher stands- I have Sound Anchor stands that are 24" high. I don't know if this would affect the bass but over all it might sound better (Ref 3A makes adjustable stands to 30" high).

Hi, Put something under the stands or something between the speakers and the stands and see if raising the speakers makes a difference before buying new stands. You might be sitting in a null point, try moving your chair forward or backwards and see if your bass response improves.

You should visit Audio Circle. There is an archived Reference 3A forum there.(you can't post) Quite a bit of good info. I use a ML Depth with my De Capo I's. Speaker level connection running the Capo's full range. Depending on the source material, I prefer to have it off.