[gx470]

Macbook Pro -> Cambridge DacMagic -> Graham Slee Solo SRG II -> Sen HD650
 
With so many brands out there, wonder if this will sound alright.

 

[Abovetheair]

Only time will tell...
 
I don't think combining will effect anything honestly, try it out and see how you like the sound. If not then see what is causing not to enjoy or like the sound.

 

[Mr Joboto]

Would probably sound good, but you can do cheaper for the amp if you really wanted.