It is a good idea to purchase a vintage tube pre-amp.


Since the new one are pretty expensive and what I can afford is an old one with budget of US$2000~3000. Since I don't have much knowlege on electronics, but I have authentic listening capabilities. Is it good idea to buy an old gear of tube pre amp. around 10 or 15 years such as Audio Research SP-15 or something similar (the newer one within my budget is better of course).  I would prefer a stable, long time use gear without much trouble.
128x128faust168
Another happy owner of a Don Sachs Model 1 6SN7 tube pre!

Don will customize his preamp to ensure it integrates well with your amp, and offers a large choice of upgrade options.

Well worth checking out!
I have heard that ARC drove the tubes really hard in the SP-10 but not so hard in the 11, but do not have personal experience.  For the same money if you are patient you might find a CAT SL-1, with which I have had over 25 years experience.  It's a wonderful preamp with a first rate phono section.  All I've had to do to it is replace one capacitor in the power supply and that only about two years ago.  And I bought mine used.
Happy shunting.
Another good bargain is the Doge 8. Which is about $1500 new. As I said earlier the Linear Tube MicroZotl2 is ridiculously good for the price. Terry London thinks it is outrageously good also and uses it in his reference system. I too had a bias towards older Tube pieces until hearing this preamp. I have had used Supratek, Thor, ARC sp 10, VTL Ultimate, CJ Premier 10, precision fidelity 7a, Doge 8 and others in the budget line all the way to the CJ Art 3 and the ARC Ref 5. The purity of the Linear Tube MicroZotl2 is just amazing. When you roll the tubes it is about as good as it gets. David Berning is obviously a genius! Oh that reminds me that reminds that I had the Berning TF 12 at one time also!
Looking at the listings now there are some awesome choices in your price range such as this:

https://www.audiogon.com/listings/tube-silvercore-transformer-coupled-input-and-output-tube-preamp-s...

this:

https://www.audiogon.com/listings/tube-audio-valve-eklipse-stunning-pre-amplifier-2017-03-06-preampl...

this:

https://www.audiogon.com/listings/tube-shindo-labs-aurieges-l-tube-preamp-mint-2017-03-15-preamplifi...

Just to list a few and many others just above $3K. If you are willing to look beyond the usual suspects, ARC, c-j, etc, there is a wealth of top notch used gear out there in your price range.  I absolutely agree with Swampwalker a good pre is critically important and can really transform the sound of your system!