What Do You Think . . . and How Does It Work?

Plenty of people have built the Pluto and most reports suggest it can compete with designs costing multiple times more.

The Pluto might not quite get you to the levels of the LX521 or the Orion, but then, as things stand, not much else will either.

Given time I’d fancy having a go myself as going active seems to be the coming future of high end loudspeaker designs.

Linkwitz was one of the contemporary gurus of speaker design (think LINKWITZ-Riley crossover, etc). His site is full of invaluable info
The Pluto is an impressive speaker for its size, it needs room around it to breathe (IMO) and will reproduce details and dynamics. What it won’t give is the full scale of a large orchestra -- no small speaker will do that -- but it acquits itself better than most (the small ATCs, well driven, being another contender -- to my limited knowledge).
Are you considering it?

A bit unrelated but look at his recommendations for speaker placement and how he uses a different speaker placement for a speaker with a different radiation pattern. I think this shows nicely how speaker placement "calculators" are at best approximations and why you need to adjust the speaker (and acoustics if possible) to match the room and speaker.

Must be half a dozen times now I've suggested people build a sub from ABS, lay it on the floor or stand it in a corner. Hsu made a sub for cars that was little more than a pipe with a driver at one end. Its physics- the pipe is a good shape, cheap, easy, and favors the physics of acoustics. On the inside its shape is strong and resists vibration. On the outside its curves diffract and disperse. What's not to like?

i heard these speakers at AXPONA a few years ago.  it was in the madisound room that sells these kits online.  
very incredible deal for the $230 for the kit less the PVC piping.  in this case they used minidsp for the active crossovers.  
sound was deep, rich and had very good bass impact. not the last word in midrange transparency though.