Most transparent amp you've heard?

Atmosphere puts it well......"Ultimately transparency turned out to be "a lack of audible distortion, which would otherwise mask detail".
I have the Halcro DM58 Monoblocks which have ultra low-distortion as their main aim. I also have the Halcro DM10 Preamp. The reduction in distortion with the insertion of these amps was certainly beneficial to the overall 'transparency' of the total system, but it wasn't until I reduced those remaining distortions by inserting the ZYX Universe cartridge, the Raven AC-3 turntable, the Continuum Copperhead arm and most importantly.......the Duelund VSF capacitors in the speaker cross-over, that a blissful purity of effortless sound could project from the system's speakers.
To listen to most other systems now, I am painfully aware of the low-level distortions which are present. Atmasphere knows his 'onions'!

Thanks for the replies.

I'm going to RMAF this year. Here is a list of amps I want to audition.

ASR Emitter 2 exclusive
Atmasphere MA2 mk3
Audio Research
Bolder 2060
CAT JL2
FM Acoustics
Halcro
Parasound JC1
Pass XA.5 and X.5
Rogue Zeus or Apollo
Spectron
Wolcott not sure if they will be there

Is there anything else I should look out for that will work with my Innersounds?

I know audio shows are not the best way to audition gear but most of the stuff I'm interested in is not represented here in Seattle.

Just remember that they have a decreasing impedance with frequency and (to quote soundstage review);
"These speakers can get by with amplifiers of modest power ratings just as long as the amplifier is stable into capacitive low-impedance loads."

In my opinion, the tubes amps on your list that have the best chance of handling the load of your speakers are the CATs (I owned them) - they can drive most anything (the Atma-spheres might work,I own them, but less than ideal IMHO), but you will still proabably be best served with SS (I owned the XA.5s are they are truly great sounding SS amps). Another tube amp that is neutral and would be able to handle the load would be the Music Reference RM9 Special Edition which is able to increase output into dropping impedances and puts out 160-200 watts depending on the tubes you use; if you use the 4 ohm tap the wattage drops a bit.

If you audition the Spectron, also have a listen to other leading class D amps. . . JRDG 312 and Continuum 500 in the Soundings/JRDG/Sumiko Suite, and Mark Levinson No. 53 for example. G.