Anyone running a Sumiko S-10 subwoofer for music? Impressions? How about Hsu ULS-15?

I have considered both these subs. On paper, the Hsu ULS-15 is the clear winner. But the Sumiko integrates perfectly, according to one reviewer (S-9)
I now have a Rel Storm 3 in my system which I have enjoyed for many yrs now. I have a rather large space to cover due to an open floor plan with 15x20 LR w vaulted ceiling opening to 12 x12 DR with std 8' ceilings. I love the way the Rel integrates in my system and don't want to give that up. This has me looking at others in the Rel line. However, Sumiko, (which was the Rel distributor for years) also makes subwoofers with similar specs and size. This causes me to believe that they have much in common with the Rel and at a better price. The Sumiko S-10 has 12" woofer (down firing) with 12" passive radiator (side firing) & 500 watt class D amp. All the other Sumiko S series are similar to the T series Rel. However the S-10 has similar components and specs as the Rel S-5 SHO which gets very good reviews. So I am considering jumping on the S-10. But I cannot find any reviews on the S-10.  Thus my post 
Anyone with experience with the S-10? I have seen many Hsu ULS-15 reviews, mostly from Home Theater users which leaves me questioning its musical integration ability. This leaves me leaning towards the Sumiko S-10. Thoughts?
BTW, main speakers are Silverline Sonatas (Avalon style)
@ttocs I now have 2 of the Sumiko S-10's. Fantastic subs. Goes deeper than my Rel Storm 3 which was a great sub in its day. I too had a hum which I had to overcome. I found the fix on Rels website. It was not the cable coax in my system. I can tell you how to fix it if you need the fix. Give me a shout if its still humming.
Like you, I'm very glad that I bought these.
I currently have an S.9 which is being powered by a Rotel 1592 purely for music. I'm planning to add one more S9 which I will use for movies and partner with S55 Polk Audio floor standers. My AV space is about 25-30 square meters with low ceiling barely 6 feet in height as it is located in the attic. Do you think it is practical to add one more Sumiko S.9 and run dual subs for music? I've heard the SVS PB/SB 1000, Polk's HTS, B&W AW610XP, but I went for Sumiko S.9 as it really performs in par with a Rel T9i which unfortunately is beyond my budget.