Best subwoofer match for Pyramid 7.7's

I have a small system I have set up in my office which consists of the 47 Labs Shigaraki integrated, Wavelength Proton USB Dac with my Mac Pro. I found a great pair of Met 7.7's and I am looking for a good sub to use with them. Did Sequerra make a single sub for those speakers (I am familiar with the 8W's) or have folks had good experience with any other subs out there for use with these speakers? Any info/insights appreciated.
REL has always impressed me. Plenty of nice tight bass and easy to make it seamless into any system I had. Another one that worked well with a small system I had was the Focal SIB sub. I'm a fan of the 8 drivers used in the subs
Post removed 
Thanks-very helpful. Will look into the brands mentioned.