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.
wcc10
When you get 40 to 50 hours on the Modi, it'll be much closer to the final sound.  Oh, I should ask what kind of RCA cables you have on the Modi.  In my experience anything that is fine strand copper I don't care for.  It may seem counter intuitive, but cables based on solid core individually insulated copper are truer to the signal.  

Something like Audioquest Forest or Golden Gate, or Morrow Audio MA2 RCA cables should help.
Will keep in mind the hours on the unit.I had Marrow Ma 2 Speaker & Interconnect cables. I didn't really care for them even after 200 - 300 hours of use. Of course I wasn't using them with the Modi 3 DAC.
Interconnects now are Signal Cable Copper.
Sounds like you have the cable issue well in hand then.  Have you mentioned what your amp and speakers are?
Amp is PrimaLuna Prologue, Speakers are Wharfedale Linton (new version). I sold a pair of Tekton Design Lore floor standers to purchase the Lintons. Much better sound stage and sound okay for the money.
I've got to do something different with this laptop. This old HP Win7 just ain't cutting it. Keeps freezing when HD gets hot. I reformatted it the other day but Hard Drive is toast.