Do I need upgraded power cables?

If you are asking the question, the answer is no. 

There are times though (especially in dense musical passages) that the sound is stage is a blur - as if of all the instruments are coming from the same place.

A good power conditioner can sometimes help individual images pop by reducing noise.  Here’s an EQUI=CORE 1000 if still available you could probably get for $600 I’d think. 
https://www.usaudiomart.com/details/650092255-core-power-tech-equicore-1000/

Also, how are your speakers positioned relative to the back and side walls, how far apart, how much toe in?  Speaker positioning can also be a big factor in improving imaging and soundstage.

People knowledgeable about electricity will tell you a power cable is a power cable and won't make any difference. People that are members of the church of audiophilia will tell you the differences "aren't subtle" (a favourite). 

 Maybe my components aren't audiophile enough to justify purchasing upgraded power cords. 

You won't know until you try it. Do you buy from dealers, or used? 

If you have a relationship with a good dealer see if you can borrow a good demo ($1000+) high current capable power cord from them, put it on your amp, plug it directly into the wall and see what difference there is. 

If you hear a difference you will have to decide whether that is worth the asking price, and that will answer your question "Do I need upgraded power cables". 

Puritan Labs PS 106 is reasonably priced power conditioner/surge protector, $1300.  Yes, I run one on a smaller system.  Patrick Cullen power cords are price/performance terrific.  Yes, I run those in the same smaller system.

Balance need be struck considering your system.  Nothing outrageous in price.  Enjoy the ride and results.  Cheers