Pros: Great sounding, excellent design and build quality from a very knowledgable enthusiast
Cons: requires impedance adapter (extra $15) for use with IEMs
That's a link to my full review. In summary:
The Fournier HTA-1 is a small hybrid tube amp. It is made by an enthusiast who sells on eBay under the name "Linear Designs". He designs and hand builds each amp he sells, and is very knowledgable about this hobby.
The sound is fairly "tubey", with an excellent soundstage. Mids are the prominent focus in the spectrum, although lows and highs are quite nice as well, and transients are startlingly good for such a small cheap amp. It easily performs as well or better than a HiFiMan EF5 when I did a direct comparison.
One minor downside is that it doesn't quite have a "black background". It is completely free of any tube related hum, but does have a slight "hiss" regardless of volume level. This his makes it unsuitable for use with IEMs, although Linear Designs will sell you a nice impedance adapter for $15 that mostly takes care of the problem. With the adapter in place, the HTA-1 does a great job with IEMs, although I still find it's biggest strength to be when powering Grados and other full size cans.