For any of you guys wondering what the differences are between the Yamaha EPH-100 and HiFiMAN RE-400, check out this thread where @modulor posts his impressions of both (and also a bit of the Vsonic GR07) when he had all of them and was able to test them.
Tricky question...I think it's harder to compare IEMs to speakers than full sized open headphones. As far as soundstage goes, the GR07s will have a wider, further back presentation, so that may be more in line with your Q701 (from memory). I feel like depth/height is presented a bit better in the RE-400 though. Comparatively, it seems more equal in each component of soundstage (more spherical to give a visual) vs the GR07 which has more width than depth/height.
@ Starfly- Thanks for that link, it was very helpful.
@ Modular- Thats an amazing write up! The sibilance you describe in the gr07 BE has me leaning towards the Re-400. Is the sub bass in the re-400 really that subdued? Also how well does the re-400 do vocals? Which is the more technical iem?