Hi Piet,
I will not be able to shed much light, I am afraid. Given the high quality of your main speakers, and if cost is not a major factor, I would suspect that the venerable Studio III would likely be superior to the newfangled B1 in your application. I have no facts to justify this opinion, but given that Sumiko still offers the Studio III, and given its much higher price tag and lower extension, I cannot imagine that it would be inferior to the B1.
Having said that, I remain pleased with my B1 and it fit my budget better than a Stentor or Studio. I am not sure that downward firing is "better" than forward firing woofers nor do I believe that home theater woofers are always forward firing. Look at the fairly inexpensive, but hugely powerful SVS line of subs made to shake rooms in HT. They have downward firing woofers and are ported to the side. "Directionality" or the ability to locate where the sound is coming from is, I believe, related more to the pitch than whether the woofer is forward or downward firing. I set my B1 on two channel music to only engage around 38 hz. At that pitch, it is not "directional" to me. Also, some claim that forward firing woofers are easier to "dial in" location wise than downward firing.
Lastly, I would like to point out that the company that bought Rel is Sumiko. Sumiko is the U.S. Importer for Vienna Acoustics and Sonus Faber. They sell very high end gear. Seems like Rel is in pretty good hands. I would be very surprised if they did not want to sell subs that complemented high end speakers like the SF Amati Homage and others they sell. Also, they were pretty responsive when I called. You might do the same and see what they tell you. At least you will be talking to them directly and may be able to get some useful information/insight. I was trying to decide whether to buy a Stadium II or III or get the new B series. I did not ask many questions relevant to your higher class inquiry. :)
I will not be able to shed much light, I am afraid. Given the high quality of your main speakers, and if cost is not a major factor, I would suspect that the venerable Studio III would likely be superior to the newfangled B1 in your application. I have no facts to justify this opinion, but given that Sumiko still offers the Studio III, and given its much higher price tag and lower extension, I cannot imagine that it would be inferior to the B1.
Having said that, I remain pleased with my B1 and it fit my budget better than a Stentor or Studio. I am not sure that downward firing is "better" than forward firing woofers nor do I believe that home theater woofers are always forward firing. Look at the fairly inexpensive, but hugely powerful SVS line of subs made to shake rooms in HT. They have downward firing woofers and are ported to the side. "Directionality" or the ability to locate where the sound is coming from is, I believe, related more to the pitch than whether the woofer is forward or downward firing. I set my B1 on two channel music to only engage around 38 hz. At that pitch, it is not "directional" to me. Also, some claim that forward firing woofers are easier to "dial in" location wise than downward firing.
Lastly, I would like to point out that the company that bought Rel is Sumiko. Sumiko is the U.S. Importer for Vienna Acoustics and Sonus Faber. They sell very high end gear. Seems like Rel is in pretty good hands. I would be very surprised if they did not want to sell subs that complemented high end speakers like the SF Amati Homage and others they sell. Also, they were pretty responsive when I called. You might do the same and see what they tell you. At least you will be talking to them directly and may be able to get some useful information/insight. I was trying to decide whether to buy a Stadium II or III or get the new B series. I did not ask many questions relevant to your higher class inquiry. :)