Hi, to answer your question, you can pair the KWI 200, 100SE or 150SE with a preamp. You can also run the KWI 200 as a straight integrated. If your source has a volume control, you can also run it straight into any of our amps, including the 150SE.
The reason that some people find benefit in pairing the KWI 200 with a tube preamp is that it sounds better. The preamp section in the KWI 200 is SS. I did this to meet the price-point.
Thanks,
Dan