Upgrade Speaker Cables or Interconnects

In my experience:
Interconnects
Speaker Cables
Power Cords

Though different cables behave wildly differently, and all cables will likely affect all these areas to some degree, I have generally found that:

1) speaker cables affect (can improve) spatial qualities of sound more than any other cable
2) interconnects affect tonal and timbral qualities most of all
3) digital cables affect fluidity and ‘analog-ness’ of sound more than any other

So you also approach the issue from the perspective of what aspect of sound you want to try to improve first. 

Again, these are far from hard and fast rules and synergy throughout all cables in a system can have the biggest effect of all. 
YMMV, enjoy the hunt.

Thanks to everyone for your responses. Some offered really good advice based on experience. Some went off the subject. Some did not read the full post!

Since my post I have ordered and received Raven Audio Soniquil speaker and xlr interconnects. The cables are breaking in as I write this update. Early reviews (after 10 hours) these cables are a steal for the price. Neutral, nice depth, soundstage and vocals. I tried cables with both tube (Jolida 3502s) and Hegel 160. Cables seem more relaxed at this point compared to Blue Jeans. Bass is better defined. Cables are a little stiff. Build, connectors are first rate. A++. I am tempted to try their power cables.

Next I will be auditioning Syngerstic Atmosphere active level 2 speaker cables. I expect to receive those cables in a few days and will update after audition.

Before you spend thousands on new power cords you might want to replace all the cheap 14-2 Romex in your house - or does that not make any difference? I’m sure there is some manufacturer out there that will sell you new wire for $500 per foot.  After he installs it, you will of course need to "break it in" so that all of the electrons lineup properly.  You will probably want to elevate the new Romex too so that it doesn't touch the ground.

If possible, run a dedicated 20 amp, 10-12 gauge electric power line(s) to your gear. I hired it done for $350. Then address your room reflections
with acoustic treatment. Glass and Hard surfaces make for crap
sound. Do not spend 10 cents on any cable or ICs until these are done.
Look out for ambient room noise intrusions also. Noisy refrigerator,
humming lights, etc. Your gear is well done so now address the other 1/2 of the equation.