I believe you have things slightly off-kilter : if you want the end result to reflect the sound you are currently getting from your Sony, you need a neutral amp.Unfortunately, that is a term which is often construed to mean 'sterile' or 'boring', but if an amp accurately reflects your source, I dont see how folk can blame the amp for being either of those things.
Most of the amps I've owned fall on the brighter side of neutral, but the uHA-120 seems closer to ruler-flat neutrality than the others. Without measurements, I'm afraid terms like 'brighter', 'warmer' etc are the best I can do, but its generally accepted that neutrality is a 'good' thing when you are talking amplifiers.
There is another issue with a player like the Sony - because you dont have a dedicated line-out, you will be 'double-amping' the analog signal from your headphone out. Like many things, I suspect that the impact of said double-amping is overstated on Head-Fi, but you might like to check with the tireless debating ('mass debating', actually) team in Sound Science - good luck with that. 