I was wondering whether CRT monitors or cell phone for instance placed in a short distance from headphones, DAC, amp, etc could create any modification and loss to the audio signal hence reducing the overall perceived sound quality ? I guess so but have no proof except what I could...

Would you recommand, to use with a PC as a source : 1) an external mono design "DAC + headphone amp" (what input and output should I use?) 2) PC -> external DAC -> headphone amp (again, with what I/O in this chain?) ? For the second option : Can I use my Audigy 2 ZS as a DAC and...