Throw away all your guilt. Do what you like.

Hey Mike, Michael here again,....What kind of speakers do you have? I have experimented w MANY subs, 2.1 system, and was very disappointed. I found a small 8” REL on Audiogon, Q-150e, that I loved w my Energy bookshelfs and now w my EPi T/E 100s. But RELs have a unique setup. They piggyback off the output of the amp, so your speakers still get full range. If you have tone controls, you can turn down the bass and turn up the REL sub. I don’t know if ALL RELs operate this way, though, but even used and small, it has performed better and sounds much more musical than all other subs, (about 6) that I’ve come across. All others have had a 10” driver. Happy hunting. Oh, and where do you live? FYI,...There are 2 Sunfire subs on Audiogon for under $400. Made by Bob Carver.

But RELs have a unique setup.

Indeed they do and their way of doing things is not the only way to get good results. They do appeal to more traditional (analog) audiophiles because they do not introduce more devices into the main speaker signal path. OTOH, the maintenance of full-range feed to the main speakers is, imho, not an advantage but a compromise.