Hi: I am looking for suggestions for a good sounding tubed headphone amp that would sound good with the Senn HD-600 with Equinox cable with rock music in the 5-600 dollar range? Thanks,Huck
Woo Audio Makes very good amps - but you must upgrade the tubes - which are pricey
I have Mapletree HD2 headphone amp with many upgrades and NOS tubes
http://hollowstate.netfirms.com/It has been my reference headphone amp - until I heard the Woo Audio 5 (with 300 B tubes) - that is a beast of a headphone amp and sounds amazing and is very pricey $3000 + ~$1000 for upgraded tubes.
I might consider selling the Mapletree or you can just call Dr. Lloyd - he only charges $100 more than the Kit - the amp holds its value and rarely comes up on used market.
Some people consider it as one of the best headphone amps -- but I have heard WA5 and it is better

There are already some good suggestions made - but do factor in price of good tubes in your budget.
edit: Dr. Lloyd used Senn 600 as a reference to voice this amp.