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.
I would have said a year ago that your best choice would have been to go used (Thor, Supratek, ARC, older CJ etc.)
This could be the golden age of inexpensive preamp! The rhumba, the Line Magnetcs Micro zotl2, the new Modwright, even the Pass headphone amp integrated does some things better than their statement preamp!
@baranyi, I'd second the Modwright SWL 9.0 Anniversary Edition which is $2900 mspr + $300 for the optional phono stage (with the caveat there are no balanced connections). The Backert Labs pre also looks like a bargain.
                 They are both great pieces! I conflated a couple of preamps in my last post. It is the Linear Tube MicroZOTL2 ( which I have on order and obviously thought was sensational) and I'm sure Line Magnetics must have some tasty offerings in that price range. Terry London who is a great friend and a reviewer for Home Theater Review has written about most of these. 


After using a Accuphase C275V SS pre, I find my old tube amp. sounds much better with thick, solid, string which unlike SS's thin sound reproduction. I think, I'll try to find a bargain good tube.