Darkhaven, I recently purhased a used Headsix. You can find my impressions in the "Another cheap amp thread..." thread I posted here:http://www.head-fi.org/forums/f105/y...69/index4.html
My understanding is that sonically it's a cut above the others amps you mentioned. I think you mentioned having reviewed Skylab's amp roundup, and it his highest-rated amp in the price range. Like you, I had read some things that turned me off to the Boa, and I thought that it would be overpriced with the euro-dollar conversion. Plus, I had some concerns with its stock opamp.
Other reading suggests it's in a higher class, as well. It seems fairly unique in that it uses the AD8610 opamp. When I researched opamps, trying to feel my way around in this new technical area, the 8610 was called perhaps the best opamp for portable applications. I'm sure this is a pretty subjective judgment, but in addition to its sonic qualities, it's low-current, so battery life should be a strength (100 hrs on a single 9v in the Headsix). Since I travel with this amp, I don't want to worry about a rechargeable battery. Even if internal charging is possible with an amp (so that no discrete charging dock is required), a wall wart takes up more space and weight than an extra battery will. Plus, I don't have to worry about degrading performance over multiple charges possibly affecting my sound. The construction is awesome, too. I love the brushed-aluminum look.
As far as "options" such as crossfeed, soundfields and such go, well, there are different schools of thought. Pretty much any extraneous circuit is going to be a potential noise source, so some purists avoid those altogether. I myself prefer to listen to CDs at hom via Pure Direct on my denon amp, which bypasses video and DSP circuitry and even shuts off the LCD on the front of the receiver
. I must admit, though, that as an IEM user I was attracted to the idea of crossfeed. Some folks hate it though, and since I hadn't ever found listening without it fatiguing, I decided to forgo it in the interest of the best "pure" sound available on my budget (I paid $130US for the Headsix, when the top of my considered range had been a $125 Mini^3 from Rockhopper.)
I did note some crackle when adjusting the volume control, but I don't think that comes standard.
It's a used amp, so perhaps the volume pot received a knock when the PCB was slid out to make an adjustment to the gain at some point in the past. Note that the crackle goes away when you stop adjusting the volume; no noise is introduced into playback. When I crank the amp all the way up with no source, there's a just-perceptible hiss in my UE super.fi 5 pros, but no noise at all at less than 3/4 volume.
By the way, the Headsix is a low-profit version of the XXS, identical but for branding; you can find partial specs for the XXS on the Meier homepage, here: Meier-Audio
. Sonically, speaking, I don't think you'd be disappointed. I'm not
an authority, since this is my first headphone amp -- and at any rate, you should take the word of a product's owner with a grain of salt since they are always tempted to justify their purchase -- but I'm a pretty good critical listener, and I like this little thing. An example: I'm listening to Muse right now. Previously, I've never liked them, but through the headsix, some of the fatiguing aspects of their music seem to be attenuated, and I'm quite enjoying this album.