So why are cables so important? Try disconnecting them and see if you still get music. Okay that's a stupid answer, but it still makes sense when you think about it. The power coming from the wall is in the form of AC Alternating Current. It's noisy, grimy nastiness. You don't want to make an audio signal out of that. So let's assume we have perfect power coming to our CD player. Our CD player uses a rectifier to create a DC signal which is in turn inverted back into an AC signal to be sent down the cables.
In a perfect world all of your components would be soldered together. However, that isn't the case, they have a distance to travel. So we have our perfect AC signal traveling from our CD player to our preamplifier/receiver. What happens to it while it's traveling down the cable? Lots of things. There are a few terms: Inductance, Capacitance, and Resistance. All are important in their own right. Resistance is the... you got it... resistance to the flow of electricity. If our goal is to have all of our connectors soldered, then effectively we want zero resistance so that the current flows quickly and accurate. With Capacitance, that's how a cable filters the signal and stores energy. There are a few theories with capacitance. High capacitance often means that high frequencies are rolled off, but it also means less noise. Low capacitance means that you have a more detailed cable because frequencies aren't rolled off. Well why would you want either? If you have the proper design, you will be able to have low capacitance AND low noise. Inductance is when a cable charges and releases energy, which reflects back into the cable. It's why shielding is a double-edged sword. Shielding blocks EMI/RFI, but it also raises inductance.
So there are a few paths for cable design. NEVER buy a networked cable. I know Karen Sumner of Transparent, brilliant woman, she can sell snake oil to a snake. Networks are just .1 filter capacitors in a shiny resin box.
Her cables are stranded cables. Stranded cables inherently cause inter-modulation (most cheapo cables like blue-jeans, monoprice, etc., are stranded). Intermodulation is when a signal jumps from strand to strand. With stranded conductors, each strand has a different resistance. So when a signal is sent down that conductor, it is copied onto all the different strands. However, that same signal shows up at different times at the next component. This means some of the signal is out of phase, and some pieces of the signal are telling the speaker driver to move out, when at the same time other pieces are telling it to move in. Obviously loss of clarity.
Another design theory uses solid-core. This means one signal at one time and no intermodulation. Sounds perfect, right? Nope. There is a new problem that's face with Solid Core conductors. As the gauge size gets larger than 14awg, we get what's called the Skin effect. This is the tendency for high frequencies to travel towards the outside of a conductor. On the outside of the conductor they travel at faster rates. This also causes timing and phase errors. However, the larger gauge size also means more current. Current is speed, and it also allows a wider range of frequency extension.
Now there are a few other theories. Multiple small gauge, solid core conductors. If the gauge is small enough then the skin effect doesnt occur. With a solid core conductor that is isolated from others, then you also dont have intermodular distortion. Morrow Audio uses small solid core conductors without shielding.
Another idea is a flat solid core conductor. Both Goertz and Tara labs use this theory, and they are some of the best cables I've had the chance to listen to. The flat conductor is by far the most frequency-linear. This means that it doesn't emphasize any frequency, it's neutral and clear. Tara Labs cables have some of the best low-frequency extension and control of any cable i've heard.
There are even more options than this. The type of dielectric, copper/silver/gold cables, silver coated copper, etc.
Now what's my recommendation? I'd go with Goertz, Tara Labs, or Morrow Audio. All three companies make some excellent cables. I would buy cables before an isolation transformer. I am selling a custom-made Tara Labs cable right now. It was made custom using their RSC conductors and is the same performance level as their The ONE speaker cable. I'm selling it on audiogon for $1175, it's an excellently musical and detailed cable. It's called Tara Labs The EKC. Retailed for $3600 when it was being made last year. Ended up costing too much to make it so Brian Kurtz and Matt Sellers stopped making them.
Goertz is cheaper, but also excellent. I often return to my Goertz Boa MI3 cables for nostalgia purposes. I don't recommend Goertz interconnects. I'd go with Morrow interconnects or Tara Labs.
So let's take a step back to our signal path. Why do cables make a difference? Because of everything I said above. The more expensive cables use better dielectrics, higher quality conductors, and have more R&D behind them. Tara Labs uses Rectangular Solid Core conductors that are 8N pure... which means 8 nines.... 99.99999999% pure. Cheap conductors are maybe 99.9% pure. They are also soft-anealed. This means that they are one long grain. So the signal isn't jumping from grain to grain within the conductor. Jumping causes distortion. Those jumps cause vibration, and vibration is the enemy. So with a nice conductor you will have no noise, with a bad conductor you will have oodles of noise.
What does that translate to? Less noise means more spacial cues, deeper and wider soundstage by a large margin, more transparency, more frequency extension, clarity, musicality, and proper rhythm and timing. All those are sacrificed with a bad cable. Going from a cheap cable to a nice cable will be the biggest upgrade you've ever made to your system. Just try and stay away from snake oil.
OKAY onto the next question...
2. 220/240 is standard I believe. You can call and ask. I've never used it abroad so I'm not too familiar with those voltage ratings.
3. Yes and no. There are a lot of companies like BPT and Goertz that make balance power conditioners. Some people like them, some people hate them. To get a balanced unit like that, which has an isolation transformer in it, will cost you quite a lot of dough and probably won't do as well as one of the ugly jobbies you see on surplus sales.