Power Cords - Equipment Priority?

I have to agree with boxer12 and jbrrp.  Over the past 20 years, power cords have made the largest impact in my system when it came to cable upgrades (i.e., ahead of IC and spkr wire).  Depending on your box count, IME the first place the cord should go is the amplfier and a close second on your digital source (with a PC designed specifically for digital gear). 

On another point, off topic a bit, is the use of isolation transformers.  I've owned several well known PLCs in the past, but the most effective by far is an isolation transformer.  While there are several audiophile approved companies making them and audiophile prices upwards of $2K, I found a hospital grade Powervar iso xfmr on Ebay for a tad over $200.  I put in some better outlets/wire and WOW!  Line noise gone, lower noise floor, more texture, etc.and no downside.  Granted Imy amp is only 100w/ch, but larger iso xfmr are available. 

If you upgrade the power cables going from your conditioner to your amp(s), do you also need to upgrade the power cable going from the wall to the conditioner? 

Wondering if it's a case of the "weakest link" here, or if the power conditioner cable itself doesn't matter as much because of what the conditioner does to the power once it's received it from the wall, thus negating the importance of the cable from the wall to the conditioner.

On every power conditioner I have tried, including my current PS Audio P20 regenerator, I have found the cord from the outlet to the conditioner to be very important.  Prior to the P20, I had always found that putting my best cord between wall and conditioner brought my best overall system sound (with:  earlier Shunyata Hydra 8, Audience Adept Response aR6, Audiodharma Powerwing, Weizhi PR6, HB Cable Designs Acrylic and Marble).  I tried to save on that leg each time, but my ears told me differently.
My P20 really likes the massive Elrod Statement (the original version).  Not quite ready to try an Elrod Master Series on it.....