What is the right cable for B & W 802's?

Eichmann eXpress Series 2, model 4 would be a really good recommendation- model 6 even better. Awesome value!!!!!! I do think you will need something like Walker Audio HDLs to compensate for the RFI/EMF you are likely to have as a result of such long runs

I have B&W 802s in a two-channel setup and I placed the mono amps (Bryston 7 BSSTs) right next to the speakers and use a short amp-to-speaker wire. My long run (8 meters using Pure Note Epsilon V.4 XLRs) is from pre-amp-to-amp.

In reading through threads here (I recommend you look through them as well) it seems that a long speaker run is less desirable than the other.

I think you can get a good IC-run cheaper than a good speaker-run. A well-made, noise-shielded cable (XLR or RCA) can be had at any price range nowdays.

Best wishes on your project.