Need help picking a Headphone amp.

I recently purchased a Westone 2 IE phone and I love the sound that comes out. I have become so hooked listening to it, that I know want to purchase a headphone and amp for my home system. I am looking to purchase the Sennheiser HD598.

I want a really good amp, but I don't want to spend more than $400. I am looking at the PS Audio GCHA, Headroom brand, and Project Box II. Can anyone help put me in the right direction?

Buy several as you should be able 30 day return. It is fun to compare and before the 30 days is up you should have winner.
Schiit Audio Valhalla @ $350 new is my entry for this thread. Great sounding and really sounds good with Sennheiser headphones. I have a pair of Sennheiser HD580s and the Valhalla handled them quite nicely. Just right on the bass and excellent in the midrange and treble.
I heard that Schiit Audio Valhalla does sound good with Sennheiser, but I was curious about Headroom. Thanks,
You should also post on Head-Fi - lots of great info over there.

One recommendation you might not have thought of is a portable amp. Some of the best portables will drive Sennheisers very well and you could get double duty with your Westone 2 IEs. I find all IEMs benefit from amping the signal from your iPod, Zune, etc.

Look at Practical Devices XM6 (includes a DAC), Ray Samuels Audio SR-71A (amp only), or iBasso PB1, among alot of great choices.

Good luck.
Do some Googling on Little Dot tube amps. They are very reasonable, and give warm and detailed sound. I used the Little Dot II+ with my Sennheiser HD-600's for a couple great years. I eventually upgraded to an Antique Sound Labs tube headphone amp, which to be honest is only marginally better.
Van Alstine has a very nice headphone amp included in his preamps. You can save some $$ and get one of the solid-state models, since the headphone amp stage is SS (even in his tube models). Then you'd have a great preamp as well. In the end you are spending closer to $1K (if you buy it new) but of course you get a preamp with the headphone amp.

This is a general consideration, dedicated headphone amps are a bit of a boutique item but it's pretty straightforward to combine it inside a preamp chassis.

If you want to spend "real" money, you can look at Woo Audio, they make lovely stuff but it will take you above $400. Unlike the Van Alstine, it's highly unlikely that you will be able to find a used one, unless you're both fast and patient (hard to combine).