Not everyone like to walk up to change LP. Also, you have very limited selection on newer relase music. I do agree that cable is the last thing you should worry about but it is not something you should omit.
i.e. A friend of my was using 3 different $700+ (retailed price) interconnects on his system. For some reason, it made the amp sounded so so but he was not willing to spend over $1500 retailed on any cable ( because the new prices are outrageous, most us only buy used cables.) After I had him tried my version of the "amp" cable, it brought out all the openess, full bodied sound, and deep clean bass it suppose to have.
It doesn't mean you need to spend much money but you do need to take that as part of your system components.
I won't comment on what brand is better for your system unless you already develop a reference point.
Power cords is more tricky than other cables. For the digital source, the shielded cable (Cleaner and smoother sounding)sounds better than non-shielded (Maybe more dynamic but more noise.) Keep that in mind, even you spend say $500 on a power cord, I don't think the bang for the buck factor exist. For better results, you can build the same version with pure silver and make sure that you got enough teflon insulation and gaps between the hot and neutral ( Fire hazzard ) and you should only use silver for the source not for the amp.
As for amps, it is really power dependent.
On a 14Watt tube amp, I can tell the difference between the 18ga. lamp cord vs the flavor 1. I can't tell much difference when it compared to a computer grade Belden 14-3 cord. I also can't tell much difference between that and a "X-Y-Z brand $500 cord"
I can't suggest which brand is better since I don't have a high current amps (I prefer tube preamp/amp for its openess over SS in the same price range.) Based on other folks feedback, Electric Glide power cord, TG Audio silver, and Elrod seems quite popular.
As for Speaker cables, deep, clean, open and full bodied sound is what I would look for. It is true that most of cable met this requirement will probably cost a bundle ( $500+ in the used market) However, if you have high effciency (92db and up) speakers then the speaker cable is less important. I do own a pair of 80db and another pair of 94.5db speakers. A good speaker cable would improve a lot more on the 80db speakers. However, a cheap and bad cable sounded muddy and distorted even on a 94.5 db speakers. Those cables should only be used for night clubs and not for home.
Just my 2 cents