I think you would be ok with a pair of VK60's. I would have reservations with a single amp, however, unless you are at moderate volumes in a smallish room. I use a Belles 350A (250/ch) biwired with the 3A Sigs and a pair of 2Wq's. Even with this combination, I feel the speakers sound better with power and a high damping factor. My room is about 16x23 and power really isn't an issue because I listen at moderate volumes but power just sounds better for whatever reason.
I have not heard the 3A Sigs with the VK60's but I did hear them numerous times with the 100w/ch ARC 100 mk.II and mk.III amps. A single amp did not sound as good as a pair biamped.
Give it a try if possible. The Vandy's do sound good with tubes. I know the VK60's are reported to be a fine sounding amp.
I have not heard the 3A Sigs with the VK60's but I did hear them numerous times with the 100w/ch ARC 100 mk.II and mk.III amps. A single amp did not sound as good as a pair biamped.
Give it a try if possible. The Vandy's do sound good with tubes. I know the VK60's are reported to be a fine sounding amp.