Does usb dac improves headphones?

[mindmenglish]

my setup: laptop>usb dac>rca>amp>speakers

i'm sure the usb dac improves the speaker's sound. but if i plugin headphone onto the amp's jack, does the headphones gets benefit from the usb dac too?

not planning on getting headphone dac.

 

[Vladimir]

List what gear you use with exact model numbers and we can actually give you info without rubbing crystal balls.