I use a HD/Emerald combo on a typical maple/basswood Premium RG through a Mesa Mk V, and the HD sounds phenomenal. By far the best bridge pickup I've ever used for shreddy prog rock music.
The Emerald is really good too, and one of the commonly recommended pairings, along with the VHII, for the HD. It sounds especially sweet when running the neck in parallel coils, and gets both beautiful cleans, as well as a really great blues tone (especially through a nildly breaking up Vox).
That being said, and this may apply to the HD?VHII combo as well, I have a little trouble balancing the output between the Emerald and HD when moving between the bridge and neck within a solo. I've adjusted pickup heights, and still sometimes find the need to use the Mk V solo boost to nudge it into the front to keep pace with the bridge. I may end up trying an Alnico Cold Sweat to match it a little better, as that was suggested by their tech team for getting a more powerful and focused neck tone for my style of music. I really, really love the sound of both the VHII and Emerald in the neck though, so I'm worried I may miss it a bit, matching output problems and all!