I have a D30Pro and you won't do any better with audible difference. The A30Pro is really great, and also have the A90 and A90 discrete. All of which will be an upgrade, but the original A90 is my favorite. Simple to use, and the sound stage is bigger than the A30Pro (even though that has full power on all connectors which is a plus). The discrete is good, but not worth the extra money unless you need the features. Digital volume control is ok, but when you have low gain mode it's not an IEM issue. Using the Simgot EA500 now on the SE side and half volume in low gain mode, it's perfect.
The A70Pro has even more balanced power if you have to get the Hifiman He6se, but that needs a 5 volt DAC more than anything else. The original A90 I'm on sounds amazing in detail and soundstage, you'll be happy. Apos still has a couple of them with warranty, the one I got from them just came in today.