Since nobody is chiming in here, I might as well add some commentary, whether relevant or not.
I ran a Bat VK-500 w/the BATPAK for quite a while, and preferred it's sound to many top notch SS amps that I also owned and compared side by side: e.g. the Plinius SA-102, Ayre V-5x, McCormack DNA-500, and a CJ 350. During this time, I also owned the non-BATPAK version of the latest and greatest BAT VK-600, but the VK-500 was ultimately more musical and better in every way than it and all these other amps. For the $$ on the used market, the VK-500 is a great deal!