This chart is pretty handy for plotting your preamp future.
http://www.prostudioreviews.com/mic-preamp-graph.html
 
It doesn't include all the available preamps (!)but it will help you sort out which ones you are aiming for.
Michael

nice chart.  that was cool

Glad you liked it. I think so, too! I would love to see it updated with more preamps listed on it.
There's one for mics, too.
http://www.prostudioreviews.com/mic-graph.html
Michael
 

those graphs are really old,
but most of those preamps (and mics) are still 'best of show' or valid today.
 
there are new preamps that were not even suggested at the time of those reviews (dates back almost 12 years now)

AT
Whether all the bells and whistles on the TB are worth it using them once or twice on a song are a question only you can answer. 

I pretty much constantly have all the switches set to the same position on my TB-12. And I can't say with a straight face that I'd be able to tell the x731 opamp apart from the x18 in a blind test (under normal non-clipping conditions), much less the steel/nickel trannies or the vintage/clean capacitors.
 
Go to Zenproaudio.com and check out the Clip-a-Lator. Gives you some idea of the order of magnitude of the impact such electronic components bestow upon a signal.
 
What sold me the TB over the WA is the form factor (I've come to hate half-rack units), and the output attenuation knob which gives me all the flexibility I could ask for in a preamp! You can dial in some nice edgy fuzz with the vintage settings (tone button in, x731 opamp, steel tranny and vintage caps) and overdriving the input, without clipping your converter!
 
Sven

Yes, sven, most (?) of those differences are subtle. The output attenuation is a biggie and for me, getting closer to a Hardy M1 was a selling point, though I did buy it and a WA76 used. The deal was too good to pass up.
 
Rob. I use those old charts as a reference, to "place" preamps/mics that I am considering now, even unlisted new ones. I was glad you mentioned your A Designs. I remember seeing it when it came out, but never checked into it, till you listed it as one of yours.
 
I find it easier to recall things visually, so the chart is "my speed".
 
Michael 

If anyone is interested, I went with the Warm Audio WA12 and have been mightily impressed so far.  It produces thick, rich, detailed sound on every source I have tried.  The DI I'm getting out of it for bass is especially delicious, but as my vocal pre it is also lovely.  This isn't saying much as I'm just a home hobbyist, but other than guitars, it is the nicest bit of gear I own and it sounds it.  I am a happy camper.
 

Once you've spent some intimate time with a good preamp you get it.  Once you hear it you understand what people are talking about (and yea, some of it is pleasing placebo).  It is subtle but real.  And once you start getting good sounds out of it, you have a certain comfort that the hardware is not going to let you down or cause a problem and realize a great weight of questions have been taken off your shoulders - is it the hardware?  It ain't and there is nothing between you and the sound except you.
 
happy hunt'n!

AT
It is subtle but real.  

I could definitely hear the difference between my AT-2020 and my new/used AKG C214 mics, but that's it.  I know the C214 is an improvement and I now have to move on to improving my vocal performances and my mixing.
 
Of course, that won't keep me from trying out a tube preamp for some more subtle enhancements:)

Good discussion here!
 
@sven450, you made a great choice in my opinion. I have the Warm TB and I'm amazed at dimensions this preamp adds to a mic'd source. Those preamps could sell for much more and I think most people would understand a higher price after using one. For the price point the folks at Warm chose, it is affordable for all of us to have a boutique preamp sound.
 
As mentioned, the ISA One is also a keeper.