I used a Audio Research Classic 60 with my 2Ci a few years back with absolutely no problems. Given the size of your room any tube amp over 35 watts with a good power supply should work. Obviously more is better, but it's a starting point if funds are an issue.
How many tube watts for Vandersteen 2's?
In an 8 x 12 room for jazz, female vocalists at moderate volumes how many watts? Is a VTL IT-85 enough, I'm using a YBA Integre right now and it seems okay but I would like to try tubes