I just faced the same decision. I have Mcintosh LS-360 speaker and was trying to mate them with a sub. I know the Internet brand subs always get great reviews but my speakers retail for 7k and I wasn't sure if those subs were up to the same quality. I suspect that they may well be performance wise considering the specs. However, I enjoy looking at my speakers as well so aesthetics was also a factor. I've spent a lot on leather recliners and the best gear I could afford and don't want to look at a large tube sub and I don't think there's anything wrong with that. Before I purchased my speakers, I spent a lot of time listening to everything around my price point. It took about a year and alot of travel. I was looking for a speaker that could enable me to hear accurate pitch changes as I find that the inability to hear them destroys the illusion of reality for me since I listen to so much live jazz here in New Orleans. The Martin Logans speakers were some of the absolute best at this. Stats are extremely fast and for any sub to blend it must be as well. When a bass guitar is playing with Martin Logan Odysseys, you can clearly hear the bass change in pitch with good rock recordings. When the Martin Logan Descent was added, the bass was seamless. The only difference was more bass so I'd highly recommend the Martin Logan sub. Velodyne subs have consistently gotten high praise. I do know that of the many dealer's show rooms that I have visited, the higher end surround system will almost always feature a Velo sub if that dealer carries the brand. However, if the dealer has a second room more geared to music, the sub is usually Rel or another brand. I decided to stick with a Mcintosh sub because I was assured by Mcintosh that with proper placement the sub would blend perfectly, the demo that I heard did in fact blend perfectly and the dealer that I purchased it from offered to allow me to return it if I was unhappy. There is no substitute for a great sub. My music is more dynamic and "realistic." I certainly advise you to take the time to find one that matches your system. I would addtion the Dynaudio sub if possible but if it's just been introduced, my experience is that it will be months before it's shipping but sometimes the best decisions require patience. A great sub is just not for movies. I'm told that almost any full rande speaker will have less intermodulation distortion when paired with a sub. My first priority is music and at least 80% of the time my system is being used it's playing music. You need to know everyone's biases.
