What qualities stand out in really good solid state preamps?

RE: non-clicking volume control - the problem is that you waste a lot of what the preamp circuit can do. The only way to get the most from your preamp is to use the volume control to control gain. That means resistors. All the best resistors are discrete, so you need to select different resistors for each volume level. This means clicks.

There is a reason why Kondo does it that way.

@bigkidz 

Changed out generic Chinese rotary selectors (tvc) for Amtrans, changed out  generic metal film bias resistors for Takman carbon film, Nichicon FG bias caps for Audio Note Seiryu, Kaisei out of stock, probably would have used them if in stock.

The best sounding pre amp out there is no pre amp at all, many fine source components can be directly connected to a amplifier, at one time I was only into CD's so I had a CD player that had a volume control on it and balanced outputs! I had 2 pieces of gear and was buying the finest CD's I could get my hands on (XRCD). 

Matt M    

     P.S I prefer a hybrid setup using a Manley Labs Jumbo shrimp and Chinook Phono pre front end with a McIntosh MC352 double balanced solid state amp. 

If a listener desires influence from a preamp on the source material (the music as it was mastered), it should be proportionate to influence the kit downstream of it offers. I assume this is the “synergy” perpetually discussed - small to moderate influences of different artifacts in the playback chain syncing up to the preference of one or more listeners. Believable even if not particularly demonstrable. 😉
e.g.: If you want clear-of-artifacts like a Benchmark (preamp) but then run your ZZ Top tracks through a power amp with Shuguang tubes*, you probably keep people guessing in all other life matters, too! 😆

*that’s no dig at Shuguang tubes - in the right rig they’re great fun

In addition to whatever switching you need, and volume control, the preamp's job is to effectively control impedance between your source/DAC and your power amplifier including the cables.   High input impedance and low output impedance does that.  With today's digital sources, preamps in our systems hardly need gain anymore, with the exception of phono sources. 

Most preamps affect the sound one way or another.  Whatever you like about the sound of your system, choose a preamp that enhances the sound and moves it in the direction you enjoy, without screwing it up.  You will know the right one when you hear it.

In my system, I like Steve McCormack's SMc Audio low or no-gain preamps such as the VRE-1 in whatever iteration, which could include the VRE-0.5 or an old TLC-1 that has been upgraded/rebuilt by SMc Audio.   I have tried other SS preamps including Tom Evan's Vibe/Pulse II, Ayre preamps, GamuT D3i, Muse Signature, and the AVC preamps, Acoustic Imagery Jay-Sho and icOn 4Pro.  The Tom Evans did nothing wrong and the AVC preamps were nice sounding and interesting, but the SMc preamp I own is by far my favorite.