Yes and no, in my experience. With the stock, unbalanced 3.5-mm cable, a powerful portable amp such as the iFi hip-dac boosts the bassy nature of the 99 Classics instead of taming it. I've seen different reports with the Meze silver cables, both balanced or unbalanced, saying the bass is tamed even with powerful amps. I don't have either of the silver cables for direct comparison.
My TempoTec Sonata HD Pro and Qudelix 5K, which both seem to have about the same power output, keep the big bass of the stock, non-amplified sound signature when using the 99 Classics straight from a phone or laptop or with the Apple Lightning DAC dongle. But throw the hip-dac at it with stock cables, and I think it overheats the already warm bass signature of the 99 Classics, even in low-gain mode with the Bass Boost turned off. All of that power isn't needed and is too much to my ears.
Now, if you're a basshead (which I'm not) ...
P.S.: The hip-dac is a GREAT match for my HiFiMan HE-400se International and Sennheiser HD 560s.