Preamp with Aleph 5 and Thiels

I have an Pass Aleph 5 amp and Thiel CS1.6 speakers and using an Aduio Research SP9 mk I but with upgraded caps and diodes. This preamp sounded fine in an older system but I was told the impdeence of the Aleph isn't a great match for the SP9 and I find that I would like more warmth, more "tube magic". I know the Thiels don't match well with bright electronics so... do I go for an ALeph P preamp? I am very intrigued by an ARC LS 5 or LS 22. I don't need phono. Any help on what preamp might work in this system?
Please forgive me for working around your initial question, but, as good as the Aleph is, I can't help but wonder if it's the right choice for your 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.