Should I upgrade my speaker cables?

Check with a local dealer. Often demoing cables is a lot easier than equipment. Good luck and let us know how you make out. 

Heimdal2 is not a low tier model, it is the low end of the higher tier Norse2 series.  As such, it uses the same materials and tech as upper Norse2 models.  You don’t say how long they are…it matters.  Kijanki spelled it out…he must be a physicist…so if your speaker wires are under 3M I’d say you are getting what Nordost has to offer.  You can try some Transparent Ultra or Cardas Cygnus if you want a mellower balance, at the expense of $$$$ and maybe a little clarity, or as the Bris call it, insight.

Look into Townshend Audio's F-1 Fractal speaker cables. They best most everything and they are reasonably priced. I have a pair that replaced my Straight Wire Crescendo's and the improvement was more than significant. Their Fractal interconnects are also fantastic. 

One set of Heimdells 2 is 4 meters, the other set is 3 meters,  that is what my dealer had available at the time, to be honest 2.5 meters is all I need.  I’m starting to hear It’s not a bad idea to to just keep the Heimdells, I found a gauge converter calculator and 18 strands of 22 gauge translates to 10 gauge all together 

Those fidelium cables caught my eye, what you guys think of them?