What preamp between Burmester and Krell?

I also agree, for your setup I think a tubed preamp, such as an Audio Note or a Lamm LL2, would be a better choice. The Krell and Burmester would, IMHO, sound a little threadbare in your system.

I would second the advice given by Al, both in this thread and the other. Passive bi-amping is not easy to do well, and why spend all that money to use a fraction of the power in the Burmester. You might consider using the money aimed at the Burmesters to try a different amplifier with more power to run your speakers full-range (or maybe the Burmesters by themselves). If you're really convinced to try biamping, you should try to find a preamp with two pairs of outputs (I don't know if the Krell or Burmester units have that capability, but many preamps, including the Lamm LL2, do).

My point on the preamp was more a practical one--if you have one set of outputs from the preamp, you will need some type of a signal splitter between each channel of the preamp and the two amplifiers being fed by it. While such devices do exist, they can be seen by some as degrading the sound. My experience has been hearing a slight improvement when I used a second output from my preamp vs. using Monster dual-headed RCA adapters out of a single output (we converted an unused input in my Shindo preamp to create a second output).