Thanks for the review, Project86.
I had both the HE-400 and HE-500 in for evaluation for the past couple of weeks. I ended up keeping the HE-500.
Enjoyed both headphones and agree with your comment that some would prefer the HE-400 over the HE-500. To my taste, the HE-400's were a little bass heavy and a bit too warm.
I've been thinking about a new cable and pads for the HE-500 as the stock pads are OK but not great. Not sure which way to go with the cable yet. I've checked out Toxic but was not familiar with Cable Pro.
By the way, congratulations on the new addition to your family!

Yes, thanks for the great review sharing your perspective of the HE-400 headphones! While it will be a bit challenging at first in regards to your life / baby / hobby balance, do keep in mind, you'll need to have a little "get-away" time here and there. It seems like the HE-400 headphones will be just the ticket for enjoying your favorite music as well as relaxing from all the other activities in your life.
I don't have a lot of headphones at the moment, but I do have the modified Fostex T50RPs, the HE-400s and the HE-500s. To me, when I put the HE-500s on, it just seems to provide a slightly better and more refined sound. However, for me, this is not a reason to sell off the HE-400s. The HE-400 also has its own qualities and stands out very well for its price point. So, I'm keeping both HifiMAN models and really love the two of them when I have time to enjoy music. When more privacy constraints are present, I switch over to my Fostex headphones, which are an amazing product for such little cost when combined with a small additional amount of money to perform the updates.
Good luck with all the adjustments your wife and you will have with the new baby. A new life in a home is a big adjustment. My "little" baby will graduate from high school in less than two weeks and head off to a University in mid-August. She's our only one, so while she's away, I will feel fortunate to have my hobbies to fall back on. Music is a big anchor in my life.

nice read. thank you.
by the way, is that the stock earpads of the he400? looks alot better than the previous velour and leather pads. i didn't find any info from your review though.

Great review, thanks.
After I build/buy another amp capable of powering these, I think I'll save up for them

Thanks for the comments everyone! I do think the HE-400 justifies its place in my collection, even though it is currently sitting next to a bunch of $700-1300 headphones.
Dyaems, I did mention in the review that these pads are not stock. They are from a Denon D7000, modified by Lawton Audio with extra stuffing. But the stock pleather pads are actually pretty nice on their own.

How would you describe the sound quality of the Earcandy cable vs. the stock?

John, thanks for the great review, it seems that these will be my next headphones =).

John, thanks for the great review. I'm curious, though - how does the HE-400 do when amped by the Grant FidelityTubeDAC-11?

Great review John, thanks for the mention and pictures of my cable.

How does HE-400 compared to a Fostex Modded?

Have you tried swapping your current pads with the new velour pads from Hifiman? From what I have read the sq changes a whole lot for the better (highs, mids, bass and soundstage). The guys at headfonia seemed pretty ecstatic about the changes that they heard when using them with the Hifiman HE-6, HE-500, HE-4, etc (http://www.headfonia.com/new-hifiman-cable-and-pads/).

Sorry for no replies - I missed these newer comments somehow.
I don't really know how the CablePro Earcandy sounds over stock - I never use the stock cable. I dislike the stiffness of it. But it's a really well done cable from a really talented and experienced designer, so take that as you will.
The Grant Fidelity TubeDAC-11 does a good job driving the HE-400. It's not the last word in refinement but gets you most of the way there for a great price. Using the adapter to tap the tube outputs does not sound great though - better to use the normal headphone jack.
Compared to my Smeggy Thunderpants, the HE-400 is totally different. Much more of a big, bold sound. But that's an unfair comparison because every Thunderpants or modded Fostex has its own unique character. Mine happens to be pretty neutral and I like it that way.
I haven't tried the new velour pads yet. I'm really pleased with the modded Denon pads though, and don't anticipate swapping them. They give me a great soundstage, much better than stock, possibly due to the angle.