STREAMER

I would definitely use one.

For a U1 mini or U2 mini, an external linear power supply is probably a more cost efficient first step. I had a T2 with an SBooster, and for me, it was a significant improvement.  

To the original question, yes a PC can certainly make a difference you can hear. It's up to you to figure out which one floats your boat at a price you can live with.

I would suggest the lending program from thecablecompany.com. For a reasonable fee, you can demo multiple cables and decide for yourself. If you choose to buy, your rental fee applies to the purchase. If you don't hear an improvement at a price you're willing to pay, you're out only the rental fee.

I've been down both paths, and currently have an X1 with an aftermarket PC.

Please let new cords break in so you don't pre judge. It does make a difference.

Yes absolutely, especially on digital sources where controlling external emi noise is crucial. 

I was skeptical of pc impacts until I did a blind comparison with a group of both hobbyists and casual listeners.  Was comparing stock pc's to midrange Nordost (Frey 2, Heim 2) cables on Luxman M900U monos, Luxman C900U pre and Esoteric N-01XD streamer/DAC. 

Even the casual listeners noted better "clarity", especially with vocals and individual instruments, with the upgraded pc's.  I was frankly surprised by the repeatability of the results.  For my system the priority for improvement was pretty clearly the monos first, streamer and then pre.

As noted, my comparison was to the stock pc's, I still question the "linearity" claims by many of the cable makers but there is no doubt for my system that cables can have an impact.

Ultimately you need to do a comparison in your system to determine if the upgrade cost is justified for you.  One suggestion I would add, however, is to do the comparison with cables that represent a major step above your current cords.  Doesn't mean you have to go with those but will help you determine if pc's make a real difference.

Good luck...