BAT preamp owners

I was wondering if anyone would be so kind as to enlighten me on the differences between a vk 3i and vk 30 pre. I am thinking about adding some tubes to my system. I currently have an aragon 4004mk2 amp and altec lansing iconic horns. I sometimes switch out the aragon for a classe 10.
Any help would be appreciated. Also if you have switched to another pre please let me know. Thanks in advance, Larry
* living in cleveland no chance to demo.