Can SMPS based preamps/amps sound organic ?

I don't have solid answers for you, but I do have an experience to share which I believe is a partial answer. 
I wanted a better dac that got me into better ES9018 chip.  I purchased a kit and did all the work.  After speaking to an old friend who is fairly well known years gone by as a competent designer,  he convinced me that done right, there was nothing wrong with a switching supply.  Being a beyond frugal,  okay, cheap person,  I had found a TV/DVD switching power supply that had the exact voltages that I needed for my dac.  I purchased this,  put it in,  fired it up.... IT WORKS... Fast, smooth, but had a glare that I couldn't deal with, waited for weeks to break in.  Still glare.  Took it to my buddies house,  he took measurements,  measured again and ended up building a filter network for the power supply.  Wholey Moley what a difference.  Glare is gone,  detail improved, weight/authority.  I became a happy camper quickly. 
Another friend purchased a Pass/First watt clone that Nelson offered up on DIY.com..  My buddy told him the same thing... Again, DONE PROPERLY a switching supply is fine,  even on a traditional amplifier. In his case,  he had already purchased 2 transformers and ran that direction.  I'm a speaker guy,  but I'm sure one of the amp guys out there will chime in and tell you why. 

My Jeff Rowland 625 S2 uses SMPS and it's the best, most natural sounding amplifier that I've ever owned.

Jeff Rowland uses SMPS for low noise. That’s why he uses them in applications where efficiency is non-issue, like Capri preamp. SMPS got bad rap from crude computer applications but when is done right is extremely quiet. Most of linear power supplies are in reality primitive switchers that switch at 120Hz at the peak of the voltage causing transition noise that propagates thru the amplifier. In addition 120Hz ripple is difficult to filter out thus requiring big electrolytic caps. These cap, in series with the signal path (circuit closes thru them), are inductive and slow down response. Power transformer has to be huge at this low frequency. Modern SMPS switches at zero voltage/ zero current at frequency that is inaudible and easy to filter out (Rowland’s 625 SMPS switches at 1MHz). It has fast response time and is line and load regulated while linear supply in power amps is not. Huge transformer is replaced by small ferrite one that can carry the same power at very high frequency.
Benchmark replaced linear supply in their newer DACs with switcher while their new 132dB S/N ABH2 amplifier also has SMPS. SMPS can be quiet not only electrically but also acoustically being free of buzz and with AC/DC operation, often in wide range.

http://jeffrowlandgroup.com/kb/questions.php?questionid=145

SMPS issues got sorted out a long time (decades) ago. These days a properly designed SMPS should be as quiet or quieter than a conventional supply.