Liquid Amps

This is definitely the most liquid looking amp. It is the Von Gaylord Uni. 
http://www.bigpicturebigsound.com/high-end-audio-ipod-he-2006.shtml

Try a hybrid amp. Tube front end makes a difference.  

@atmasphere explains well why it's a little tough to find "liquid" SS amps.

However, there are many issues with tubes too.  I have both SS (McCormack, McIntosh, digital amps, and others) and tubes (ARC Reference), so it's not like I'm prejudiced toward one or the other.

While people are offering nice suggestions and commentary, they are jumping the gun.  We must first know what speakers you are using.

Many speakers have a definitive preference toward tubes or SS.  Thus, any recommendation is primitive without knowing what speakers you are using with this amp.  20 SS watts won't cut it on certain speakers...conversely, certain high power or high gain SS or digital amps will have problems sounding "liquid" with certain speakers (i.e. horns). 

It's actually something that can often be measured.  For example, the output impedance of a certain tube amplifier can pull down levels in higher octaves on certain speakers while boosting the lower octaves.  This could be a good thing and certainly make the sound seem more "liquid".

In short, you really have to let us know what speakers you are talking about.  In my systems, modified McCormack amp are the most "liquid" sounding with my particular speakers...even moreso than my ARC reference amps.  However, I wouldn't guarantee it would do the same for every set of speakers.  Some may like the strengths/weaknesses of tubes more than the strengths/weaknesses of SS.  (I've had Spendor speaker in the past that loved tubes far more than SS.)

All this being said...I don't think the BIGGEST problem with systems not sounding "liquid" is the fault of higher order distortion in SS amps.  I don't think Atmasphere made the claim that it's the "biggest" problem either, so we may not even disagree per se.  I just want to point out that IME the biggest problem with systems not sounding "liquid" rests with the speakers and source first...not the amp.

It's really amazing what can be accomplished when you get the right pair of speakers and feed it an impeccable source.  An amps strengths/weaknesses can still be apparent, but it become obvious that it's not the driving force behind problems unless you have a really poor amp (or poor combo with a preamp). 

If you're doing digital, the biggest impact on liquid sound is getting rid of jitter.  Focus on the server/renderer even more than the DAC nowadays.  If you're doing vinyl, you probably already know how big an impact the cartridge and phono preamp can make.  Address those things first before thinking a "liquid" SS amp will solve your problem...it can only do so much.

@labtec  Couldn't agree more about the modified McCormack amps.  I recently had a new driver board, wiring and jacks installed by Steve and Co. The sonic performance far exceeds the price for the upgrade.

Regarding your comments about listening to vinyl, the phono stage makes a tremendous difference.  My 25 year old Aragon 47k was pretty much spent as it introduced a persistent hum that I found objectionable.  After seeing how many really inexpensive phono amps are on the market, I thought I would give a Sutherland KC Vibe a shot.  It is a new design from Ron Sutherland and based on his dedication over the years to phono stages, I thought I would give it a shot.

I gave it a few weeks of persistent use to break in and it just was incapable of opening up and revealing the soundstage that I knew was on my recordings. I would call it's performance in my system, "matter of fact".  The notes were there but no subtlety, no ebb and flow and again a greatly restricted soundscape.

I had a very productive conversation with Josh at MusicDirect.  After discussing my system and what I perceived as the Vibe's shortcomings, he suggested the Luxman E-250.  I then researched Luxman and found few reviews, but what I did learn about the design seemed in concert with my listening preferences.

Upon receiving the Luxman for a trial, I also purchased the Cardas burn-in LP with isolated bands of pink noise to facilitate burn-in of the new gear.  The Luxman is a wonderful sounding piece.  A big ball of sound can be heard around the speakers.  Great tight bass with kick drum slam.  Incredibly clean treble with wonderful detail.  Now, this is a $2300 unit, so it should sound better that the $895 KC Vibe.

Lesson learned.  Don't insert a component into your system that is not up to the quality of the rest of your gear.

Boniojo (sp) is now dead his last gasp ampzilla  had power supply issues if I recalll. Is the Co still around?  Serviceability is always a factor when dropping that kind of change on an amp.

It’s like searching for something you can’t have.  Have you looked up the  meaning of Audiophile?   I’ve come to believe we really are all afflicted.   Easy solution: get  a kt150 driven tube amplifier and enjoy the liquid.