REL Sub T1 or T2 Good Match for Dynaudio Focus 140

My experience, and that of my dealer's, is that the T series are better for music. I am using a T2 with some upper end Dynaudio speakers and I am very impressed. See if you can try one at home, but I highly recommend the T2.

The Dynaudio Sub 250 is indeed a very nice sounding subwoofer. I owned one and used it with my C1's and if you are able to use the high pass filter option that may work well for you. However, I can tell you that in my house the REL T series is even more invisible and musical than the Dynaudio Sub 250 when used to augment the low frequencies only for music playback. The REL connects via speaker level and the blending is seamless. I love Dynaudio and think they make amazing speakers, but for 2-channel music listening, the REL in my opinion is the better choice here. See if you can try them out in your home first and form your own opinion.