I have been pondering this, as most speakers are 4 or 8 ohms it would not be too difficult to either have removable filters or a set of relays to switch between filters. Looking at the Tripath app notes the diff between 4 and 8 ohms is 3 caps per channel. I would guess that 90% + speakers used will be 8ohm too.Quoting myself fom a different post : What's the big deal here. I have 8 ohm speakers for years now and will probably have them for another 20 years . My ( pre ) filter is designed for 8 ohms , so fine and flat response here, no roll off in the highs .If I ever buy new 4 ohm or whatever impedance speakers to replace my current ones with the same quality , I have to spend at least a couple of thousand dollars . Replacing my output filter with high quality inductors and caps to match the new speakers impedance will set me back at least 12 dollars per channel
Still waiting for some A & B test between the Hypex UCD and a quality IRS2092 , for instance a LJM L15D with some 5 Dollar cap upgrades .
Never heard the UCD modules , but did hear a lot of good amps and own a few very respectable class A/B and one class A amp and still impressed with the L15D , it's my favorite every day amp .