1. In general, a well constructed purpose-designed device, like a headphone amp, will be superior, for driving headphones. Note, they have a much lower input impedance than that of the average amp. Of course, such a general statement is irrelevant when you get to real-world specifics.
2. Just because it's loud enough does not mean that it has enough power to work into that load without distortion. A 12 o'clock setting is pretty high (in general and without knowledge of your preamp or the gain curve of the pot). Is that where you set it to feed the amp/speakers?
3. Why not just try a decent headphone amp and see for yourself if it is better? Surely, there are web dealers with a useful return policy.
2. Just because it's loud enough does not mean that it has enough power to work into that load without distortion. A 12 o'clock setting is pretty high (in general and without knowledge of your preamp or the gain curve of the pot). Is that where you set it to feed the amp/speakers?
3. Why not just try a decent headphone amp and see for yourself if it is better? Surely, there are web dealers with a useful return policy.