Many of the current show reports have raved over the WP with a full BAT setup. I think it was in the Absolute Sound that one of the reviewers who was not normally a Wilson fan was wowed over the combination.
The BAT premps especially the latest crop are outstanding. I did a demo with the older VK 51Se vs The VTL 7.5 and the BAT has better dynamics, better top end and a tighter bass. The VTL was believe it or not a tad warmer. The newest series of BAT preamps keeps all what was good and now the BAT preamps are a bit warmer and full bodied sounding. Design wise they are some of the best preamps out there.
As per amplifiers the big VK 600SE is incredible sounding, caveats you should leave it on, and use good power cords and good conditioning.
I did a comparison of a well set up VK 600SE vs a pair of $50k Krell mono blocks and the big BAT was as good in most respects other than the Krell Monos has an even bigger presence and deeper bass.