Pros: High-powered, great sounding OTL design
Cons: Not ideal match for low-impedance dynamic-driver headphones
This is not a full review, just a rating and a few comments. I bought my WA2 used, and was really surprised how good it is. The WA2 is among the better headphone amps available. It actually surprises me that it's not even more popular than it is.
The WA2 has some pretty impressive power delivery, and it works wonders with high-impedance cans like the Beyerdynamic T1, and is also remarkably good with the Audeze LCD-2 and HifiMan HE-5LE. Only very low impedance dynamic drivers, where the damping factor could be an issue, and not in the WA2's sweet spot. But with the T1, the WA2 is absolutely stunning.
The WA2 is an outstanding headphone amp, and the fact that it has multiple inputs adds to the string value.