Ok here is that review on the AE5 soundcard from kitguru:
https://www.kitguru.net/components/soundcard/dominic-moass/creative-sound-blasterx-ae-5-review/3/
Guy reviewing it has AE5 soundcard, Sen HD650s and also Fiio E10K, Schiit Stack comprising the Magni 3 as test comparisons, here is his main bit about the comparisons of the AE5 headphone amp vs the rest of the equipment;
His thoughts
"So, with that out of the way, let’s begin to fully dissect the audio quality. I will start by saying the overall quality is very good for a £130 PCIe sound card. Compared to my Schiit Stack, I would say the overall audio presentation is slightly smoother and less forward – so the bass is slightly more prominent while the high-end has been tamed a little bit. I don’t think the overall differences in sound are huge, but if you are a keen music junkie then you should be able to spot the difference between the AE-5 and what you normally use.
Compared to the Fiio E10K, however, the differences are much more subtle. I already think the E10K is warmer than the Schiit Stack (which is ever-so-slightly bright in its presentation), so to my mind the AE-5’s sound is quite similar to the Fiio. With the HD 650s I was testing with, that means the overall sound is very fun and enjoyable, definitely not analytical or overly harsh.
I do like a bit more detail in the high-end, though, but the benefit of a PCIe sound card (with software) is that you can tune the sound to your liking using EQ. As such, I was able to just add in a slightly more forward sound to the AE-5, which just helped break through the HD 650s veil"
So he feels the AE5 is similar to the E10K (many around the net suggest SMS m3/X6 is similar to E10K) but he does say he prefers the bit more detail, I assume that's from his Schiit stack with Magni 3.
Am still tempted to grab an 2nd hand Soundblaster AE5 for 84 quid of rainforest but decisions....