Upgrading power cables

when it comes to power cords, i like to upgrade the amplifier cord first.. the amp is the most power hungry of all plus i like to make sure i'm not short changing everything in front or behind the amp source with an amp that's not getting enough electricity.. 

Treadman, the range of improvement that cab be achieved is quite varied in different ways...

• Very modestly priced components, like my Schiit Bifrost DAC, achieved a significantly higher level of performance with good power and interconnects nectcables
  
• Higher resolution components tend to exhibit more modest levels of improvements, like my Simaudio MOON phono stage. But then you start to hear an improved level of refinememt i.e. resolution
  
• My Naim 5i amp, having the best power supply of all, probably exhibited the least amount of improvement, but again, the level of refinement or resolution has exceeded my expectations considerably.
  

So even though the individual amount of improvement may appear to differ, the overall improvement of the system justified the investment in power cable upgrades for all components in my case.

Regards

Thanks for so many informed responses!

I agree with upgrading the source first. But, don't discount the importance of a good PC on the preamp. The preamp influences the timbre of your system, especially a tube preamp since tube rolling can change detail, soundstage, dynamics and colour.
 
Finding the right PC for your preamp can influence the sonics dramatically. One thing to keep in mind is that the preamp is a low-current draw component and many aftermarket PC's have heavy copper windings more suited for an amp, so

Since you are thinking of upgrading the power stage, I'll second the recommendation of adding a dedicated AC line (if possible). This line will provide you with cleaner, more stable current, since you will now be isolated from the rest of the devices in your home.

For me it was the CD player, somewhat surprisingly.  Long time believer in interconnects and speaker cables, i never gave much credence to the idea that power cables could make a difference.  Last year i started experimenting.  First, i replace my stock cords to the monoblocks with Nordost Shiva cables--more and better bass.  Then i replaced the Shivas with Aciustic Zen Tsunamis and used the Shivas for my CD and preamp--still more bass, slightly better soundstaging.  Very happy with my system, i thought i was done.  I got a deal on a used Nordost Vishnu, just one step up from Shiva, so i did a little A-B test.  With the preamp, no real impact.  With the CD player--WOW.  Slightly more bass but better soundstaging and air and space around individual instruments--really noticeable, for the first time.  Could be system/component dependent, but if i were to start over, i'd start with the source first, then the power amps.