I would like to say that I have had the upgrade made to an SA-5000. The total package cost me $3150, including a mint used SA-5000. I decided go this path because I wanted a 6922 based pre-amp, I wanted a detached power supply, and I wanted the tube count to be low. This eliminates quite a few pre-amps. Also, Mike's facility is close to me so I could hand carry the unit.
My direct experience with other pre-amps is with a C-J PV-5, owned since new. In my system the PV-5 with Sylvania GB 3-mica 5751's is lush, rich and coloful, with a good soundstage. But I was having to use silver IC's to raise the hi-freq's up out of darkness.
The stock SA-5000 easily trounced PV-5 w/Sylvania GB's. The SA-5000 had more air, better control of the bass, and more specificty in the mid-range. This was with Sovtek 6922's.
After the upgrade, there was more of everything. I can hear the "intent" of the musician better now. On certain recordings, the soundstage kind of washes over the ceiling of my listening room. The imaging is more continuous front to back, top to bottom. Bass is tight and defined (I am using SS amps).
This is a great little pre-amp to experiment with 6922/7308/CCa's with. You have one each for the line stage, and two in the power supply, along with a 6CA4 and a 12AX7. (The phono stage uses 2 6922's, also.) Each tube contributes its own sonic signature. I've settled on Siemens 7308's in the power supply, and Amperex 6922's in the line stage.
Whether spending $3000-3500 for a "rebuilt" pre-amp is of value to you, only you can decide. This is a physically well-built unit, with a floating circuit board. And I've come to really appreciate the tube-based power supply.
Also, it really looks cool in the dark with the covers off, and the 6CA4 glowing.