I think I'd probably love the Genelec 8351, but the price of one is almost as much as a pair of HEDD Type 20. I can't compare with the Genelec, but the Type 20 has 300 watts per driver. I wouldn't think the 8351 with 150 watts for the low end could have the transient response of the Type 20.
But, yeah, I'm with the OP. I can't quite understand how the Type 20, especially, isn't getting more notoriety. Its compact size (relatively) for a 3-way monitor is perfect for small-ish studios. I'm at about 1 meter distance, and they sound superb from normal down to very low listening levels. And although I don't monitor at loud volumes, they seem able to scale up with plenty of headroom, without any compression or distortion. And I can't agree that there's too much separation between the drivers. I mean, they're only physically about 1 to 3 inches from each other. Put your eardrum level between the 3 drivers, and at a little over 1 meter, I don't detect any audible separation. Pin point accuracy in the stereo field, and clear as a bell without a hint of distortion.
I previously had Event Opals (I still do, but they're in storage now), and loved 'em. But the Type 20 does everything they do, but with more clarity and detail throughout the frequency range. I thought I could easily hear and detect differences between produced releases with the Opals... but with the Type 20 the differences, detail, and clarity are magnified to a much greater degree, and without any harshness, while being highly entertaining and great to listen to.
I love these things. I always wanted to get to a 3-way monitor eventually, so I could have an option of doing some pseudo-mastering on the side. I thought I'd like the ATC SCM25, but was afraid of a lack of low end, and the price was a little out of my range. Then I accidently ran across the Type 20s. And once I started reading up on 'em… they sounded like a perfect fit for me. So glad I took the plunge and splurged on these. Well worth it in my opinion, and, yes, I'd think they should be more widely known than they seem to be.
To the OP... it'd be great to just change the thread title to something like "Talk about the HEDD Type 20 or 30" and make this the official thread in High End... since there should be one, and there isn't... until now!