Low Cost DACs

Currently I have my laptop connected directly via 1/8 jack from headphone outlet into 2 RCAs directly into my tube amp. Quality of sound is lacking to say the least!
I am considering adding an inexpensive DAC ( iFi AUDIO nano iDSD LE Portable DAC  or iFi Audio nano iOne DAC ) into the stream between the laptop & amp.My question is: will this influence the overall sound I'll hear out of my speakers? Will adding such a DAC help to increase the quality of sound produced by the system?
I'm not interested in spending a lot of money on a DAC as this is a source that I don't use as much as some others already in the system.