Looking at these specific preamps give me your opinions

sls883:  Thanks!  The Telefunkens might be too bright in my system but I will listen a bit to how the LTA sounds from factory, then jump for those or the Siemens, depending on the effect of the LTA pre to the overall sound.  Love detail but don't want too bright. Cheers.

Take a look inside each of them and then tell us what you see?  Parts, transformers, AC chokes, capacitors, resistors, volume control, and what designs they are.  Once you begin to look inside and learn about design, you decision will be come much easier and you will understand what makes sound quality.

Happy Listening 

@brbrock - +1 on the LTA Microzotl preamp with the level two upgrade offered by LTA. Fantastic preamp! 

Revelation Audio Raven would be my choice from your original list. No question. A highly regarded designer who has keenly refined the circuit topology and parts list. These things are important. Nay, critical, essential.

People often refer to the weight of a unit as a sort of shorthand for indicating the quality of the design. And that can be useful.  But it is a rather crude measure.

I'd be looking for point to point wiring and the use of 6SN7 tubes or similar (6J5, 6SL7, for instance). These tubes are regarded as classics for a reason. That is, they sound really good.

Of those preamps, the Raven preamp without question....but I'd add Aric Audio preamps to the mix, especially the Motherlode or Motherlode XL