Good small sealed subs are expensive.
Also typically small subs are rubbish either because small driver and/or if ported high freq port tune
37hz frequency response is poor for e9f. My main speakers go lower than that.
Try to maintain a sense of perspective.
The task here is to help a noob pick their way through a minefield of options so they can make a "best in category" purchasing choice.
Sitting on the sidelines commenting "that sub isn't as good as main speakers" without including that they're pretty hefty floorstanders with 8 mid/woofers between them and an original RRP of £3,500, it really isn't that constructive. This isn't a willy waving contest.
Yes, yes... I know you didn't pay £3,500 for them because you bought them used. That's not the point though. You're not making valid comparisons.