That's a tough one... with its particular signature (deep bass, warm tone, minor midrange recession, and fairly smooth up top) AND better all-around performance there's nothing I can think of except some customs - the Westone ES5 and Heir 8.A come to mind - and even those tend to have a little less bass overall. If you're okay with taking a cut somewhere - for example in bass quantity - and not expect an all-around upgrade there are other options. The Sony XBA-H3, for instance - it doesn't really have a clarity advantage on the EPH-100 but is an upgrade soundstaging and treble quality.
I tried the original (mk1) ASG-1 but the performance wasn't great. Never managed to get my hands on an updated version or the ASG-2.
The Ostry KC06 that
ZapX629 mentioned is what comes to mind for sound (but not necessarily build). It has a brighter, clearer signature than the warm and smooth A63, but has a similar midrange focus. Costs $55-60.
I compared them a little here: http://theheadphonelist.com/brief-impressions-vsonic-vsd3s-ostry-kc06-havi-b3-pro/
Unfortunately I haven't tried the Noble 4 universal but the custom one has a very different sound than the LUF-4 - very flat and smooth and relaxed. The LUF-4 has a more v-shaped signature with more aggressive bass and upper mids/treble. The GR07 actually falls between these two in sound signature so you're moving in different directions from it depending on which one you go with.
Haven't tried any Fischer Amps products.