Which is the better decesion?

Have been thinking of a PC change for my Integrated amp (Classe Cap 151) and was trying to use my money in the best choice selecting between Synergistic Master Coupler, Black or Blue but... (there's always a but!) aside from which PC would be better to improve the sound stage and depth as well as finding more inner details with my  ARC CD3 Mk 2 (has a good PC) and Apogee Slant 6.
I listen to Alt Rock, rock and a verity of blues and others. NOW, I had also considered a small power conditioner as I already have Shunyata Defenders on each outlet. Given a choice of only a single outlet would the most frugal choice be the PC as opposed to  having to change the integrated or the power conditioner and where does it provide the best bang for the buck on a constricted budget?
There is a much better choice than a power conditioner but at $1k is probably more than you are ready to spend right now. And do not buy a cheap one, that will be money down the drain.

The Synergistic power cords you are looking at are the industry standards for value. I still have a Master Coupler in my system. And it is a pretty high end system. https://systems.audiogon.com/systems/8367

Since you mention depth and inner detail then keep an eye out for deals on HFT and ECT. Both are great at making speakers disappear. Check https://highend-electronics.com 

If you buy a new amp or whatever you will get some improvement, yes. But frankly maybe not as much as with these. Also things like power cords, HFT, ECT, etc are more or less forever. No matter how much or what you upgrade to down the road you keep them and use them with everything. So its smart especially when on a budget to work on using things like these to maximize and get the most out of what you have before spending on something new.
WOW!!! you sure do have a high end system, very nice! The 2nd part of my question concerning power conditioning would refer to changing a Defender for an Audience unit and at which place would be deemed as a placement? Thank you, with this going on it leaves me way too much time to ponder that 1 change I can force to consider.