I have a BAT VK-20 and BAT VK-200 what are the bes

Who knows, unless someone experimented with that setup. That said, I had a Vk30 and Vk200 and found that match to be a bit dark, adding an Acoustic Zen Silver Reference II was a very nice addition.

Contact the Cable Company and audition Nirvana S-L or, better yet, S-X Ltd. Not inexpensive but if you're patient you might find some for sale on A-gon.

I've owned a VK200 for over a year now and really like it. I had aVK3i mated to it for about a month, but for the last nine months or so I've been using a Blue Circle BC21 preamp instead.

I experimented with different configurations of Acoustic Zen cables - Silver Reference II and Matrix Reference II - from DAC to pre and pre to amp. Eventually settling on two runs of Matrix Ref II. I use the AZ MC2 from transport to DAC. In my case, using the Silver with the Matrix or two Matrix depended on what tubes I was using in my DAC - Silver Ref counteracting dark tubes, and Matrix Ref taming revealing tubes.

All the Acoustic Zen cables I've owned are very smooth and throw a huge soundstage. Choosing which one to use depends on your taste in playback and what you're trying to achieve sonically.

What cables are you using now and how do you want to change the sound?