USB cables and Galvanic Isolation


I've seen that some Dac manufacturers tout having galvanic isolated usb ports.
Does this mean that the Dac is immune to noise/jitter generated by a computer usb port connected to it?
And will a special noise isolating USB cable be required in this instance?
I've seen a lot of threads touting audiophile usb cables and at present I'm not using one.  I am using an Amazon Basics usb cable from my computer to a Peachtree DACitx.  I have been thinking of upgrading the Peachtree as it was my first external Dac which I am happy with but curious as to how much of a jump in SQ I will hear with a newer more expensive DAC. 
Although, I'm not disappointed in the sound I'm getting from the computer, after reading on-line forums that computers generate a lot of noise and mess with the sound I'm a little leary of usb audio.
nicktheknife
For those that are wondering I am mostly an analog guy but am interested in building up my digital front with possibly streaming in the future.  I have just been playing cd's and files downloaded on my laptop.
My system consists of a Rogue 99 Magnum Pre, McCormack 0.5 power amp, JVC XL-Z1050 cd player used as transport to the DACitx via rca, Oppo BD-103 for SACD playback, PBN DP loudspeakers and mostly DHlabs BL-1 interconnects. As I said, I'm using a laptop with an Amazon Basics USB cable to the Peachtree DAC itx for playing files. 
 I won't complicate things with the analog front end.  
If you listen to (read: read) Dow Jones here, nothing matters, nothing makes a difference, all snake oil, blah ... blah... check out all his posts. You will learn nothing. That's the reason he exists. His hobby.

Do yourself a favor, and try a nice cable. Even if entry level from Wireworld or AQ, or Triode Wire Labs. You may be surprised. We can talk all day here, but nothing is substitute to actually trying.
I've made up my mind that I will try a better quality cable.  No harm, no foul.   
Except the question is which one?  
Any max. length as far as usb cables go?
Hopefully Dow Jones will not report this one and get it deleted:

Length does not matter, but preferably short. About 1-1.5 meter no longer, if your equipment proximity allows. 50 cm would work well too.

As for which one, depends on budget. Examples: entry level Wireworld, AQ, Triode Wire Labs, Supra, Sablon
I've tried Kimber and didn't notice a difference of course I had my wife switch between the expensive and generic cable to eliminate bias. Try the DH Labs you mentioned.