OK. . so I've had about a week to really listen to them and I really like them a lot. I don't have much to compare them to other than an old pair of Sony V600's and a pair of Senn HD580's as I mentioned earlier. I'll try to do a mini review, but it's my first review so be gentle.
Packaging
I received the HE-4 and EF-5 combo in 2 boxes that were bundled together with a rice bag(at least that's what I call them as that's what rice from Asian food markets is usually contained in) and taped together solidly. There was no damage to the boxes and it took about 5 days to get to me from SE China. Not bad considering it shipped right before Christmas. The EF-5 was well packaged in thick foam with nothing moving around. The HE-4's come in a nice presentation box with all the cables wrapped in thin foam.
Build Quality
The EF-5 is solidly built and the only thing I could find wrong was that the plastic piece around the tube was a little wobbly. After 5 minutes with an Allen key and a few twists, it was all fixed. The HE-4's are very well built. You can tell immediately that they are hand crafted by looking at the stitching on the headband. Aside from that, there were no scratches or nicks anywhere. They feel solid in your hands and very high quality.
Setup
I have listened to the HE-4's in 2 different setups. The first setup is from my PC to FiiO E7/E9 via USB connection and the second setup is via my PC via Creative Labs X-Fi Titanium Fatal1ty line out to the HiFiMan EF-5.
Listening Impressions
With the FiiO setup, I had to put it on high gain and to me the HE-4's didn't really sound any different than the 580's besides requiring the higher gain setting. If anything, the sound was a bit muffled. I don't experience this with the 580's so I was a little disappointed at first.
I then switched over to the EF-5 setup. Wow!! What a difference. The sound was crystal clear and I could hear details in the music that I couldn't hear before. The bass hits low and the highs are not ear piercing. I was actually quite surprised that the HE-4's were that much better than my 580's. The sound stage is broader as well and I just feel more enveloped in the music.
Conclusion
I am very pleased with the HE-4 and EF-5 combo and it has replaced my FiiO and 580 setup as my primary listening configuration. I have an Audio GD NFB-11 on order so hopefully it will improve things even more. For anyone looking for a "step up" from a 580/600 type headphone, I would highly recommend the HE-4's. To me, they offer a good "bang for the buck" as compared to the HE-5LE and HE-6 headphones out there. I would have loved to get the HE-6's, but just couldn't justify $1k for headphones.
Follow Up
I decided to take the E7 out of the picture to make it more of a apples to apples comparison. Here's what I found after listening to a variety of songs back to back. The E9 can drive the HE-4's just fine, but there is a small difference with the EF-5. The EF-5 brings out just a little bit more detail and sounds a tiny bit fuller. So it appears that the muddiness I was hearing was due to the E7 DAC. If I didn't have both to compare back to back, I would say that I would be happy with the E9.