If you use the line-out to A5, you are using the X7 DAC, and gaining more power (and I assume cleaner) for driving larger, more inefficient cans. If you go the Q5 route and use coax/optical out of X7 into the Q5, you use the DAC in the Q5 (bypass X7 DAC) and gain whatever benefits, if any, it provides over the X7 and then uses the same amp module as the X7 to drive your cans. Again, the X7 has a fine DAC, I would go the route of A5 and use a player like neutron to give you more flexibility to tweek the sound. I use the X7mkII with a Shure KSE 1200 IEM and the sound quality and detail that it provides me are unreal. It is 90% of my home unit. For my portability needs, I am done chasing "better" as I cannot see gaining anything significant over what I have or need sound wise. The X7 buggyness is another issue. Again, you did not mention what cans you have or what you are trying to achieve. Your "Better sound" statement needs to be clarified as it is ambiguous. What is your kit currently? What is it lacking to meet your needs? PM me if you care to. Good luck hunting.