Senn 600 are fairly easy to drive. There are many excellent choices. As per Goober's advice, head over to headfi.org and you will find a wealth of information. Depending on the type of music you listen to, there are tons of choices.
Check out some tube headphone amps coming out of China. If you search hard enough, you can find awesome deals. I have been fairly impressed with the ones I have personally listened to. I currently own one (Consonance Cyber 20, SET amp) and am waiting for another one traveling through Pacific Ocean. (Cyber 30, another SET amp). One caveat is that you need to replace those cheap Russian tubes with some decent NOS tubes, figure another $50 to $100 on top.
All I will say is that the US distributor is adding like 200% markup on these nice amps, and they can still compete with other amps at those price ranges. Another great amp to consider is Cayin HP-100A (yet another SET amp). All these amps are excellent with female vocals and small jazz ensembles with traditional SET magic, not too good with orchestral work or rock. I haven't try too many other types of amps yet.
You can see my review on Cyber 20 located at headfi.org. I was using Senn HD600 with Cardas cable for that review. My other headphone amp is a tube hybrid from Italy, Rudistor RP5.1cav (US$1500) which is more balanced sounding. Shelter 901 vs. Koetsu Rosewood or Amperex 7308 vs. Mullard 6922 tubes would be good analogies between the Rudistor and the Cyber 20.
FrankC
Check out some tube headphone amps coming out of China. If you search hard enough, you can find awesome deals. I have been fairly impressed with the ones I have personally listened to. I currently own one (Consonance Cyber 20, SET amp) and am waiting for another one traveling through Pacific Ocean. (Cyber 30, another SET amp). One caveat is that you need to replace those cheap Russian tubes with some decent NOS tubes, figure another $50 to $100 on top.
All I will say is that the US distributor is adding like 200% markup on these nice amps, and they can still compete with other amps at those price ranges. Another great amp to consider is Cayin HP-100A (yet another SET amp). All these amps are excellent with female vocals and small jazz ensembles with traditional SET magic, not too good with orchestral work or rock. I haven't try too many other types of amps yet.
You can see my review on Cyber 20 located at headfi.org. I was using Senn HD600 with Cardas cable for that review. My other headphone amp is a tube hybrid from Italy, Rudistor RP5.1cav (US$1500) which is more balanced sounding. Shelter 901 vs. Koetsu Rosewood or Amperex 7308 vs. Mullard 6922 tubes would be good analogies between the Rudistor and the Cyber 20.
FrankC