Which REL sub, R528 or B2

Go for the 528. It's an outstanding sub, easy to connect and integrate. I was never happy with the B2. Been tremendously satisfied and still own the G1x2, 505x2 and a solitary 305.
All the best

As a fellow C1 owner I have been very happy with my Rel B3. I did at first think it was slow but that was because I didn't have the phasing/timing right. I had to move it about 3" back to finally get it right. Also on a whim I bought a Nordost Baseline made to Rel spec and I after putting it in place of the stock Rel cable I heard attack and decay I didn't even know I was missing.

The thing Velodyne does good is you have almost no acoustic problems anymore. But there is a big but.......it is still toooooo slow. Instruments and voices are still too big in proportion. My PLW-15 is superior in timing. But you need Audyssey pro to get it right. It has no acoustic system like Velodyne has. Velodyne speaker units are tooooo slow in respons. This is by far the weakest point of there subwoofers. Timing is crucial for using a subwoofer in stereo. For a long time I did not like it. The PLW-15 with Audessey pro did change my thought about this. Rel and Velodyne are both not capable og giving the stealth low freq. I want and need. Never buy a subwoofer with a bass reflex system. And Never one with more than only one unit in front. All the other kinds of sub's I test did fail in speed and in respons. You always will be aware of the flaw's. This can become very irritating!!

I have a REL Q150E that is anything but "slow"...just a beautiful sounding little front firing sub that works really well. I shall continue to defend it regardless of the naysayers! Perception of "slowness" from a sub likely has to do with placement, or listening rooms of more than 10,000 square feet in damp unfurnished Medieval dungeons...like my guest house.

Bo1972 you have confused me with the "slow" comment a bit. A reviewer of Tone Audio writes "B2 was more then fast enough to keep up with these speakers (panels)" and again "it was also a great match for the Manger Zerobox speakers and that is one of the fastest speakers I've ever heard"
It must be some setup issue...