I use the Scheps on every Vocal track that leaves my studio.
Not just for the built in pre amp but the EQ section is amazing (its simple).
But the tonal characteristics are great for dialing voice detail.

telecharge

Sanderxpander
There's a bunch of things included with Sonar you could use for that, though I think none of them are called "preamp".

If you have any recommendations, I'm all ears.
 
I found this thread on KVR with a number of 3rd party suggestions.
https://www.kvraudio.com/forum/viewtopic.php?t=398612
 
It would seem the "FG-73 British Discrete Preamp" I previously mentioned is modeled on the Neve 1073, similar to Waves Scheps 73.

Well if "analog coloring" is what you're looking for there are a bunch of options like the tube leveler you mentioned, but also the Nomad BlueTubes Analog Trackbox, the ProChannel Console Emulator and even things like the CA2A, Softube Saturation Knob and Tape Emulator at mild settings.

chuckebaby
the tonal characteristics are great for dialing voice detail.

Thanks, Chuck.
 

Sanderxpander
Softube Saturation Knob

On a somewhat unrelated note, two of the guys that run PT Expert said this would be their choice as their desert island "harmonics" plug-in. I found that interesting. I know saturation/distortion adds harmonics, but I've not seen the Sat. Knob referred to that way.
 

All a "digital preamp" is doing is adding digital noise to the signal.  To my ears most digital saturation/distortion is closing the barn door after the horse is gone - although it can be useful in certain situations.  I'd never use it as a standard technique since it clouds up the soundstage too much most of the time.  I  use transformers coming in so most of my signals come in with enough fur already.  But even with clean signals, a lot of digital saturation is more a steady state artifact than a dynamic one and simply piles up fuzz in the same frequency ranges.  If you record signals clean I would save the transformer/tube saturation effects for a few tracks to make them standout against the "clean" tracks.  If you effect every track it is too easy to get a digital haze over the entire song.
 
If you think about an analog studio (not tape but analog board and outboard) there is usually not enough outboard to do backing tracks - 10-12 channels of drums, bass and rhythm guitar and whatever else is needed.  So the 1176 is used on the snare, giving one kind of edge, the bass gets a real La2a with a different tone, until all the good stuff runs out.  The toms, perc etc. run through a board, which may or not be transformer coupled or have comps (or even EQs) and don't have that special sauce.  Already your bass and snare sound separate, tone wise, than the rest of the backing tracks before you get to mixing.  If you put digital comps on every track the whole thing blurs together, tone wise, rather than giving a more prominent place to the more important parts (including overdubs like the guitar, vocals [1176>La2a], triangle).
 
But each to their own.

AT makes a good point. Additionally, I would say that the "distortion" that a good preamp adds should be very minimal. So you should be looking for a very subtle/mild effect, which is why I mentioned that specifically about the Softube knob. Once you start hearing obvious distortion, you've gone too far. Like going from one track to two tracks doubles your volume, similarly does distortion "add up", especially if you use the same plugin on multiple tracks.

+1 to what AT said. 
When I read the thread title it raised my eyebrows and my first reaction was.. what good would a plug in pre amp be?? But I can see they could be used to polish turds and whatnot. 
I'm a huge fan of only recording the best incoming signal possible with the gear you have on hand. 
If I don't like what I'm hearing before I hit the red button, I keep changing things until I'm happy. 
And a big part of that is having good pre amps on hand. Be it just your interface, a good mixing console or a few dedicated pre amp modules. To me the word "pre amp" will always relate to analog gear.  In the wonderful world of recording pre amps are way up there on my list of "important" to own. I guess I'm still sceptical of what digital can and cannot do better than analog and pre amps and guitar pre amp sims are not on my radar. 

Im not sure the digital age is quite there yet with exact replicating characteristics of a good pre amp.
We are close, but even good Guitar Sims like Bias FX and its mimic features that allow one to replicate amp sounds is a great feature but still missing some tonal quality's.
 
Im not ready to throw away my analog pre amps yet .
I almost came close to letting go of a majority of it a few years back, as I wanted to work strictly in a box. 
But it just wasn't happening. there was something still missing.
 
I don't believe its just the tubes either, its the transformers, the diodes, right down to the caps.
Software can only do so many things. your at the mercy of your PC.
 
Sorry, I might have taken this in a totally different direction here. My apology's to the OP.
All im really trying to say is (I believe) its a bit more than adding digital noise. Its the way each pre amps hardware reacts with its own living parts (hum, warmth, the grade of components) the whole 9.
 
When you look at the construction of a good pre amp, there is just no way it can be completely emulated by a board/CPU.

chuckebaby
Sorry, I might have taken this in a totally different direction here. My apology's to the OP
 

 
Not at all, Chuck. Repost it if you like. I appreciate getting input from the forum's heavy hitters.
 
To be clear, I am looking for the kind of subtlety that Sander and AT are talking about -- like the effect Craig describes in post #5 with two console emulations.

I think it's also important to define what we mean by "distortion." There are non-linearities inherent in analog amplifiers and these are more or less random. People often say that digital audio "collapses" the soundstage but I think that's not really what's happening, it's that the non-linearities between the left and right channels in analog gear expand the soundstage by creating differences between the left and right channels (thus adding a sense of width) that don't exist with digital. 
 
Another reason is that many audio interfaces have more crosstalk than what happens in an analog console, and this is typically at the highest frequencies, which are the most directional frequencies and therefore contribute to a feeling of width. I've measured high-frequency crosstalk on some well-known and popular interfaces that measures -45 dB or so, which is audible. (FWIW not to get too Gibson Brands rah-rah, but the TASCAM UH-7000 has extremely low crosstalk because they have separate power supplies for each channel, and really fastidious circuit board layouts. This kind of attention to detail does make a difference.) So something like a Console Emulator's non-linearities are perhaps adding some very slight degree of distortion, but they're also trying to "undo" the collapse that happens with crosstalk and the identical characteristics of digital data streams.
 
Howver...for a sense of perspective, because an XYZ preamp was used on a bunch of hits doesn't mean anything. I'm sure quite a few hits have used Mackie VLZ preamps. All that matters is the emotional impact of the music. If overdriving something or non-linearities contribute to the emotional impact, that's the only reason you would want to use them. I use the Console Emulator because it provides a sort of clarity that I believe does improve the music's emotional impact by giving it a slight amount of (for lack of a better term) "presence."

I like to put the Tube Saturation in front of the AmpSim(in a fxchain) in the Prochannel an use it as a preamp to the Amp Sim. I don't use any drive, I just adjust the input to a nice clean sound then I increase the output to make the amp sim break up. It sounds right to me.