I have recently bought a new sub from Arendal, their 1723 1S. They are a Norwegian direct to consumer manufacturer with distribution in Chicago (I believe) in the USA. They offer a range of both speakers and subwoofers that all come highly recommended by their customers, plus there are some very good online reviews. What I especially like is that they are designed to be corner (speaker ) facing in, plus they offer an excellent app for both Apple and Android that allows easy fine tuning and really straightforward integration. They also offer RCA and XLR inputs, plus a 10 years warranty and 60-day auditioning period, and free pre-purchase advice. I use my Arendal sub with my Sonus Faber VIII’s in a 2 channel HiFi setup. The sub is great and very musical. My only comment is they are about to release a brand new range very soon. So I’d speak to them about that timing, even though they offer an upgrade path to recent purchasers. I also looked at REL, SVS and Rythmik but both REL and Rythmik rely on speaker output for integration, which is not as flexible from a room correction perspective as that provided by Arendal and SBS. Hope that helps.