Dmg,
My twenty five cents.
I still think you can derive benefits from a stand alone budget power cable for your amp. If you want to and are able to spend the money on the gear your friend recommended, then that would likely provide greater benefits. More details below.
The Venom is much less accomplished than Shunyata's better cords - the Diamondback and up. I would say I noticed less than half the benefit from the Venom compared to their better cords for my budget CD player in a back to back test. Is the Venom better than your stock cable - most likely. Can you do better in a cost effective aftermarket cable for an integrated amp - most definitely - especially if you have no constraints in terms of the suppleness of the cord used.
Now to the comment: "First we need to get power to the wall. Forgoing that, I like to begin with an Audience Power Conditioner. Feeding an A Plus 4 square box. Now we can use much shorter cords, and you will find they make little difference if upstream is A Plus, to borrow the term."
I assume your friend is talking about the $495 Audience Adept Response aR1p and not the $3800 multi-plug conditioner, and that the "A Plus 4 square box" is a $350-$450 Analysis Plus Power Oval 10 with 4 Box. If that is the case - then that is about $900 worth of power conditioning and power distribution gear between your wall and your power cable to your amp, and a far cry in terms of investment from a $100 power cable.
With that said, putting these quality pieces in the front end of your power chain should have a positive overall effect on the sound of your system, and the amount of that effect will depend on how dirty your household power and the amount of junk coming back from your electronics is in the first place. For example, this set up may help protect your amp from digital grunge from your SACD player, even though the power conditioner is at the wall and not being plugged into directly.
But, I think you can't necessarily say that you will hear less of an effect from an upgraded, albeit shorter, aftermarket power cable used to connect your amp to pre-conditioned 4 box. If you are cleaning power upstream, the benefits of an aftermarket cable may actually be even greater since you are now protecting the integrity of higher quality power. Remember, the biggest impact from better power cables are 1) more efficient power delivery from larger cable gauge and better conductors, and 2) reduced EMF, EMI and RFI in the proximity of your electronics gear, speaker and IC cables due to better dielectrics, geometry and shielding (if applied) in the aftermarket cables that finally deliver the power to your source, amp, etc. I find it is all about system synergy, where appropriate improvements one place generally amplify or enhance the benefits of improvements previously made elsewhere. If the high quality cable on the 4 box stops three feet from your gear, then you are not applying the benefits described above nearest your equipment and other cables where they will do the most good.
Often, as your equipment and accessories get more sophisticated, "synergy" can become more elusive as changes in one piece may make your system sound different, but not always better. Experimentation and willingness to reject trial solutions that don't result in real improvements is key. That should not be the case here where you would be going from stock cables to power conditioner, high quality power box and better cable to your gear. I would guess in this case, the changes you would realize for an investment of about $1000 would be quite astounding - on the same order as upgrading your amp or source.
To summarize, while simply adding an inexpensive aftermarket cable to for your amp would likely provide improved sound, the set up described above could provide significant added sonic benefits to your system by delivering cleaner power to all of your gear conditioned at the wall and distributed via the 4 box. Even with the Conditioner and 4 box in the power chain, I think your amp would still benefit from an upgraded power cable, if only to provide 12 gauge or larger wire for the last little bit of supply (although other benefits related to reduced interference would also likely accrue). And while I really like Shunyata products, I would not recommend buying the Shunyata Venom power cable for your application, as I think you can get better performing (and shorter) amp cables for less money from Signal, Zebra and other Internet cable distributors.
Good luck.