Clear difference between Harbeth 30.2 & Super HL5 Plus?

Have you listened to them?
Looking at specs (size of cabinet, bass extension), I think you'll see partially why.  The 30.2 is their top-of-the-line true monitor.  But all I know is that at CAF, driven by a large Rogers tube integrated, they could really boogie and dig down deeper than I would have expected.

I heard the SHL5's in a brick-walled room driven by high-end Naim components, and I was surprised to find that they sounded a bit bright to me.  This would be in line with audiothesis's comments.  The 5's certainly will go down lower than the 30.2's, but that's what the 40.2 is for.  As I said, I was really very positively surprised and impressed by the 30.2's at CAF, driven by large tubed Rogers integrated.  I think a lot of the smaller speakers at CAF were being helped by bass reinforcement courtesy of the small hotel rooms.