VTL ST-150 MB-450

I had a ST-150 on my ML Ascents and really liked the sound. I have since sold the Ascents and purchased Summits. I called Bea at VTL and she said she would not recommend the ST-150 with the Summits. She said it would not handle the speaker well. She stated to go with the 450s. Has anyone compared the sound of these two amps? I have heard that with some brands of tube amps the sound is better on the smaller wattage amps.