Hi Leon,
I am a technician. I served 20 years in the Army and worked on everything from telephones to radar systems. I repaired stereos, TV's. I am also very interested in good audio systems. That's my qualifications.
Do not concern yourself with oxygen free cable or crosstalk. Crosstalk was a problem with early Hi Fi systems. It was generated from the source. From vinyl records and tapes. Also a little originated in the amplifiers. Any cross talk between speaker cables may have been able to be measured but certainly not heard. The speaker impedance is very low to effect power transfer, what tiny bit jumps across the cables is virtually nothing. Crosstalk is in the order of micro or picovolts. You need at least tens of milli-volts to hear anything from the speakers. Crosstalk is a concern with inputs to amplifiers.
Figure 8 cable is fine. Its just that it is difficult to identify the polarities.
As far as power handling its rated at about 10amps. That at true RMS power will mean 400watts into a 4 ohm speaker or 800 watts into an 8 ohm speaker. That's the limits.
For easy listening a typical speaker consumes about 200mwatts Less than a quarter of a watt. 10 watts is very loud. The neighbours would be calling the cops if you have any near. The cable carries 2.5A into a 4 ohm load. Or 1.25A into 8 ohm load.
This brings me onto the manufacturers' power rating of their amplifiers.
Such things as peak RMS pwr, Peak music pwr etc. It is all BS. Manufacturers exaggerate the output power. eg. 10 watts RMS is somewhat equivalent to 100 watts peak music power. There are no set figures unless the power is stated as true RMS power.
How I was once told how to convert to true RMS pwr from peak music pwr. Was to divide the peak music pwr by 4 add your age and subtract the current date.
All you need to worry about is what has been said already. If you use figure 8 it is well above what you need but has that polarity difficulty. That is well and good.
Dick Smith and a host of stores carry marked polarity cable. Some cheap cable that is about the same gauge as the figure 8 is easier to install. Then you can be sure to have it right. I have in the past marked one side of a figure 8 cable with red texta.
Hope that clears up a few misconceptions.
Cheers