
Hey hey this thread is hotting up. Like so many here who all have the Senn's I have the HD600 and HD650, blah blah

. The HD600 can be got on eBay for around c£110 or less. I got mine for £95 +PP and those amped outperform the HD650.
Again I am assuming you don't have a good headphone source already.
Also the Grado 125 Amped is on a par with HD600 in my opnion and are around the same price second hand. (I'm talking sound not comfort

). But the Grado's can be made to be comfortable quite easily.
It all depends on how good your source is in the first place I have heard some very good CD Players with Headphone out and own volume control sound really, really good where you don't need to get an amp unless you are talking big bucks for small gain.
If anyone lives near Telford and wants to come listen or you Paul.
I have the following you can demo till you feel happy.
I have as headphones HD600, HD650, HD280Pro, HD201, Grado RS1, Senn mx (various), shure e5c (of course you'll have to use one of the buds that don't fit me or I haven't used)

e21's sony, senn px200 and others I just can't remember
Amps, I have a very good mixing desk headphone out, Terratec sound card, EMU pro sound card and breakout box, MF v3, Project Headbox v1, Sugden Headmaster, Gracie m902, Graham Slee MkIV, Penguin CMoy amp, Minibox headphone amp, Headout on various AV and Stero amps,
Source have vinyl LP12, CD various (SACD, DVD-Audio, Marantz, even good old Ipod's).
You can compare the sound to various speakers. for small closeup comparison the B&W 805s are very good or some amped monitors.
Really if you want to listen I have no problem at all. Bring your own CD's etc and then go from there. (note some of the above used in different places of work and the rest of family).