BAT VK-60 or Another tube amp?

There are many (CJ and Rogue come to mind), but none have as much current. This is what makes the VK60 somewhat unique. However, it will not have as much current as your Pass 250. Perhaps a monoblock version VK150(?). Also, these amps are huge, heavy and emit lots of heat.

Music Reference RM-200, great detail even a low volume and throws a huge sound stage. It's a hybrid amp that has gotten rave reviews. They pop up once and awhile in the low twos, but always sell fast. Good luck!

I would go for the Cary v12 or for a bit less money the Cary Rocket 88. A steal these days are the Six Packs from AES (Cary's lower end line). I have heard good things about the Six Packs

The bat is going to sound different than your pass, and maybe that's what you're after. somewhat warmer, richer, very vibrant mids w/ highes and lows a little softer. The 75SE is a much better on the extremes, but doubles the price. Excellent staging and depth for any of the bat amps.

VK60's are pretty easy to sell, you can very likely buy one, try it, and resell it with only loosing the cost of shipping. (which at 70lbs) is 60-$100.

You're cutting your power quite a bit, for the b&w's. Depends on how big the room and how loud you listen if it's ok...I have had a single vk60 driving wp 6's and it was plenty fine.