Which pre should I choose?

Don Sachs customizes the Tubes4HiFi SP14 preamp.

The SP14 uses 6SN7 tubes. Cost depends on which options and tubes you chose; the base configuration starts at $1,699.

Upgrading the output caps to Duelund CAST PIO-Cu will set you back $375.

Upgrading one pair of the 6sn7 tubes to Shuguang Black Treasure CV181z will cost $129.

Changing one set of RCA inputs to XLR is $275.

Worth adding to your list of possible candidates. The only problem is that since each one is custom built by Don, you can’t audition it before you buy (unless you know someone who owns one).

http://www.dsachsconsulting.com/custom%20line%20stage.html

I own one and can attest that Don is a great guy and very easy to work with. He will work with you to ensure that the output impedance of the preamp matches the input impedance of your amp.

And yes, his preamp is an incredible performer!

Aolmrd 1241: Tks for your suggestions. I am afraid the vintage gear will always need repair constantly. It will cost your time and money and inconvenience.  Also, I have heard that  Tube amp. is not as durable as transister one.

Vintage gear does not "need repair constantly ". In fact it is probably better made than most modern units.  As long as any electrolytic caps are replaced you should be good to go. 

analogluvr: Tks for your opinion. One of my friend also suggests me to choose a good solid state Pre. from famous brand for the longer life than the tube one.  What I care is once the vintage has problem, whether I can get it repair and recover.......... (according to the opinion of one audio service engineer, some times, too old gear might hard to find parts which had been produced long time 20~30 years ago.