Your 501s will benefit a ton from a good headphone amp. I've got the K701s, Audio Technica W5000s and Ultimate Ears Triple.fi 10 Pros, all driven by a Woo Audio WA6 with a Holland GZ34 rectifier tube.
Lots of people love the Senns, so you'll be in good company. I haven't heard the ASL amp. If it's up in the $600 range, then you need to consider the Woo also. If you buy some Senns and an amp, then keep the 501s for a while to see if the new amp doesn't smooth them out.
Also, AKGs and most cans need 100-300 hours of break in. Use your cheap Headphone Out circuit to break them in, if you haven't already done so. The character will totally change in many cases. My Audio Techicas sounded like pure crap until I got over 100-hours on them. Most people say the AKGs need up to 300-hours.
Your ultimate goal will be to get your speaker system up to the standard of your headphone rig. Most of us think that speakers are superior, but a price point of up to 10X for equivalent performance.
Dave
Lots of people love the Senns, so you'll be in good company. I haven't heard the ASL amp. If it's up in the $600 range, then you need to consider the Woo also. If you buy some Senns and an amp, then keep the 501s for a while to see if the new amp doesn't smooth them out.
Also, AKGs and most cans need 100-300 hours of break in. Use your cheap Headphone Out circuit to break them in, if you haven't already done so. The character will totally change in many cases. My Audio Techicas sounded like pure crap until I got over 100-hours on them. Most people say the AKGs need up to 300-hours.
Your ultimate goal will be to get your speaker system up to the standard of your headphone rig. Most of us think that speakers are superior, but a price point of up to 10X for equivalent performance.
Dave