Why not horns?

Macrojack, the folded horn you asked about is one of a thousand variations on the same idea. I can't speak to that particular model but as a general design it works pretty well if done right but has a few problems. You have parallel side walls which means you have resonant frequencies and it really doesn't flow like a what I would call a true horn. If you look at mine it is expanding in all directions as you go from driver to mouth so no parallel walls and no sharp bends like in a folded design. However, the folded horn is a good compromise.

Lokie, as you realize it is difficult to describe sound but the best I can think of is a box is muddy compared to a horn. Not that good subs sound muddy but horns are just a bit better. I think it is usually described as the horn is faster but I'm not sure what that exactly means. If you could hear one you would understand but unfortunately they are few and far between.

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I love my Sansui sp-5500's MADE IN JAPAN! I had all the wires and crossover parts CRYOED

I'll chime in regarding Klipschorns.
I had never heard nor seen a pair but decided to look to buy after becoming somewhat bored with my system over the past several years. I had Martin Logans and before that a couple of models of Maggies, Paradigms before that. I just thought it would be fun to try something completely different. I sold all my stuff, bought the KHorns the day I went to listen about a year ago and have been enjoying them since. I have a few SE amps to drive them. Sound is at least as good as what I had before, and even a bit cheaper ($2K for the KHorns, with less expensive amps).
KHorns (or horns in general) might not be for everybody, but they do work well. I'm sure I'll be playing Hi efficiency speakers and low power SE amps for a long time.

You do not need 35ft long horns. Herman I also have front loaded bass horn with 16ft horn path. You also have to consider the room if rooms right the bass horn can couple to floor ceiling to produce a even larger horn. I do this with all my horn designs.

Here's a fresh question.

Are horns generally more forward rather than laid back sounding? is this always necessarily the case?

Reason I ask is that the Walsh drivers I currently prefer tend to be on the laid back side, in that most things happen behind the plane of the speaker in most setups.

That is the most distinctive characteristic of the omni Walsh driver I think. Other than tha, with my eyes closed, I believe I would be hard pressed to identify the driver technology used in that they have various characteristics of otehr driver types I have heard and read about, including the midrange purity of horns.

So part of the appeal of horns to me is that in my mind they represent the other end of the spectrum in terms of being more forward sounding than what I have. I'm not saying that is better or not, only different. I think what I have pushes things about as far as I would need to go in its direction, so horns appeal to me as a means of trying something completely different and comparing and constrasting. Were I to do it, I would also anticipate the need at some point to use a spearate amp for them from the rest of my system(s), probably a tube amp, in order to get the most out of them.