Preamp with Aleph 5 and Thiels

Output impedance of SP9 is 250 ohms which is relatively low ...or at least should have no problem driving A5 with an input impedance of 10K.

Output impedance of LS5 is (400 ohms) which is a little higher vs. SP9 though not enough to make a difference in your case.

I don't know about the Aleph/Thiels match, but I had the Aleph P with the Aleph 5 and it was a great combination. I would also consider a used Pass X-1 which is quieter, more neutral and more transparent than the Aleph P, though I never had the X-1 and Aleph 5 together in the same set up.

Thanks for the help. I already assumed that an ALeph P would match with the Aleph 5 but the question now is would the Thiels and the all Pass electronics be a good match anyway. The other question is would an LS-5 or LS-22 (or Aleph P) give me the warmth and dimensional quality I don't feel I am getting from my SP-9.

Aleph 5 has a neutral, detailed sound. Lacking body.
Thiel is also neutral, detailed sound. Would make use of tube or beefy amp to give it a fuller sound.
Personally, I'm not very comfortable with the two combo.
But ymmv.

I sold THIEL's for many years, Threshold Amps then, which were Nelson's first company, I believe.
I really liked using a tube preamp with solid state amps--to give a rounder sound, smoother upper midrange to the solid state of the Threshold.
The Pass is much more refined than the Threshold--but still, IMHO can benefit from a really good tube preamp--depending on one's taste, certainly.
Without checking for a mismatch of impedences, you may consider a cj pre, or a VAC pre with this combination.
Good luck and good listening.
Larry