The distortion levels in the bass look very similar to those in the Stealth, and especially given that you're already at Harman levels of bass then it's unlikely that you'll need to use much EQ to boost the bass, which means you'll probably be operating at the 94dB blue line or below in the following graphs (which is totally fine), so yes very similar bass distortion between the two headphones:
I like the look of the frequency response in the E3, and its uses the same "metamaterial system" (according to DCA website) that the Stealth uses to help tune the frequency response. I really like the fact that it is a smooth frequency response which is often hard to achieve with planars - it's only really DCA planars that seem to not have this "fine grass" high Q sharp variation in frequency response, instead the DCA planars exhibit this smooth frequency response that is normally the characteristic of dynamic driver headphones. In my opinion this smoothness of frequency response (lack of "fine grass") is beneficial for sound quality. The fact that the E3 is more affordable than the Stealth is a major bonus, and it's good to see. I'm probably not about to drop $1900 on headphones, but I'd like to see some more trickle down into more affordable models - just like has already happened from Stealth down to E3.
Nice headphones, I do really like what DCA are doing, I hold them in high esteem even though I don't own any of their headphones yet! (Did nearly buy the Drop DCA Open X for $399 during Black Friday though! (importing to UK re VAT and exchange rate tipped me the other way though, combined with pad replacement cost/process which would be an ongoing occurrence through the life of the headphone))