I do think it is quite funny to see how much you spend on IEMs and headphones, and how at the same time you appear to try and save as much as possible (relatively speaking of course) on the source. From hearing how IEMs scale with a better source, even cheaper ones like the Final E4000, I would be more inclined to find my "end game" IEMs/headphones and pair those with the best source in terms of both synergy and performance. I do agree that it doesn't require the best gear to get a good idea of what certain IEMs/headphones sound like, as something much more affordable will likely be sufficient. However, in this hobby I think the word "sufficient" is about as alien to us as the word "content".
So, for instance, if I were looking at the Diana V2 (instead of dreaming of one), I would also try to go as far with the source as I could and would ideally end up with the Dave. Although that also has something to do with the looks... Black Diana V2 + Black Dave...