What's next for the ultimate sound quality?

I'm reading this post quite a bit late, but I wanted to put in my two cents and ask questions, as I've been really contemplating building the 2-way version of this kit.

IMHO, the source will make the biggest noticeable difference, followed by amplification. That said, if it were me, I'd upgrade the amp first. Due to the efficiency and easy load of these speakers, you'd be doing yourself a huge disservice by not trying out some single ended or low powered tubes, as in something in the 10-30 watt range. You will be very surprised how powerful those little watts can sound on decently matched speakers. They can be had for fairly cheap on the A'gon. I found tubes to really shine in terms of 'presence'; not as pinpoint in the imaging, but much more 'real' sounding. If you want a 'tubey' sound in a solid state, a safe bet is Pass Labs. They have great resale, and sound tube-like for solid state. I'll do a little Krell bashing here. They just don't sound good to me. Very thin, analytical, but powerful. Same goes for Levinson.

It's too bad you haven't heard more gear. I'm considering getting Merlin vsm, because they suit my needs at the moment. At one point I swore I'd never get them, but I'm really curious as to how they will sound. But I really wonder how they would compare to the ZRT's, a good design speaker with top of the line components. Anyone out there do anything remotely comparative? A friend of mine has some diy monitors using Dynaudio drivers and really likes that sound. I just wonder how much "The whole is more than the sum of it's parts" applies to something like the Merlin vs. the ZRT.

the "ultimate sound" is live music. the next step is to go to concerts and not worry what your stereo system sounds like.

Gleb, you seem like practical type guy. I would suggest that if you're going to play around in tubes that you don't go all the way to some incredibly expensive amps...you can do pretty nicely with an upgraded Dynaco St-70...with mods from either Curcio, Van Alstine or Kimmel (Welborne). Honestly, although the amp is vintage, it wasn't bad at all and with the mods it compares to some stuff that's pretty expensive. In fact, a friend of mine is the rep for Zanden (make 50k amps) and he tells me that from what he sees on a day to day basis, really not many folks out there are doing very interesting stuff in terms of circuit topologies... many of the top brands are just straightforward circuit designs with high end materials (expensive caps...silver wound transformers..etc). Ron Welborne's kits are great, if you can still find them...but in the end they may not have enough juice for your speakers. If the Dyna is too mainstream for you, other nice entry gear would be a Conrad Johnson. But yes, tubes are really the way to go...I've not been able to find a solid state amp that can match the beatiful decay that tubes can give you. In comparison, solid state sounds harsh and sibilant to me now. Ok, well all the best

Oh and for your question about the next thing:

Not sure about the quality, but he's doing something innovative...

http://www.ted.com/index.php/talks/woody_norris_invents_amazing_things.html

Your ZRT 2.5 are lovely. As a singer I generally prefer smaller 4-5" drivers in small speakers like proac response and have also been enamored with electrostatics. Having read about the ZRT 2.5 and being a fan of scanspeak, I also decided to build these speakers and find the midrange to not be what I had hoped for. Wanting to preserve my investment in these drivers, I am considering building troels Ekta or Ekta Grande re-purposing the ZRT drivers and adding mids...