[Batty]

I have a pair of Sennie HD414s that I hardly use because my Copland csa-14 doesn't have a headphone socket.

I have been offered a MF X-can v3 for $150 (100 quid) is this overkill?

If I go with it I could always upgrade the phones later I suppose.

 

[Mad Max]

Aren't those 600-ohm headphones?
Have you checked if the X-can is a good match for high-impedance headphones like HD414 or the 600-ohm versions of DT880/990/770?

 

[Batty]

Just ordered a pair of Q701s