I realize that the V2 manual (
http://www.gracedesign.com/support/v2_manual_a.pdf) lists the max balanced output as +27
dB, and the max unbalanced output as +21
dBu. However, I think that's a typo, and I think the max balanced output on the V2 is actually +27
dBu. I think this is the case because balanced outputs, coming from the same amplifier circuit, are 6 dB higher than unbalanced outputs. +21dBu + 6dB = +27dBu. (this 6dB difference between the balanced and unbalanced outputs is also true with the V3, except that there's no typo in the V3 manual... +25dBu vs +19dBu for the V3).
in any case, regardless of whether or not the max V2 output is +27 dBu or ~+29 dBu, with the AD2K on minimum sensitivity (set to clip at +24dBu input), the AD2K will digitally clip before the pre-amp overloads, so as long as your levels look good, you'll be good to go.