I don't think it's possible to provide a better answer to which cable is more important than "it depends." For instance, considering just interconnects the following four variables are potentially significant:
1)Length: Obviously the longer the cable, the more pronounced its effects will be.
2)Signal level: The lower the signal level, the more important the cable is likely to be, everything else being equal. Keep in mind that the signal level from source to preamp may or may not be less than the level from preamp to power amp. For instance, a cdp with 2-volt output in a system with a sensitive power amp and speakers may result in the volume control being set very low (say 9 or 10 a.m.), which corresponds to a lower signal level coming out of the preamp than going into it.
3)Component output impedance: Higher output impedance of the component driving the cable will increase some cable effects.
4)Interconnect importance is affected by the ac power distribution scheme: If the interconnects are unbalanced (rca connectors), and the connected components are plugged into separate dedicated ac lines, or separate outlets, or separately filtered outputs of a power conditioner, low shield resistance in the interconnect assumes increased importance, in order to minimize the likelihood of ground loop issues. With balanced (xlr) interconnects, this is unlikely to be an issue.
Obviously there are many other variables that enter into the picture with respect to speaker cables and power cords.
Keep in mind, also, that "more important" does not necessarily mean that a more expensive cable will be better at that location. For instance, some very expensive interconnects have high capacitance, which is a poor match for components with high output impedance.
Good luck!
-- Al
1)Length: Obviously the longer the cable, the more pronounced its effects will be.
2)Signal level: The lower the signal level, the more important the cable is likely to be, everything else being equal. Keep in mind that the signal level from source to preamp may or may not be less than the level from preamp to power amp. For instance, a cdp with 2-volt output in a system with a sensitive power amp and speakers may result in the volume control being set very low (say 9 or 10 a.m.), which corresponds to a lower signal level coming out of the preamp than going into it.
3)Component output impedance: Higher output impedance of the component driving the cable will increase some cable effects.
4)Interconnect importance is affected by the ac power distribution scheme: If the interconnects are unbalanced (rca connectors), and the connected components are plugged into separate dedicated ac lines, or separate outlets, or separately filtered outputs of a power conditioner, low shield resistance in the interconnect assumes increased importance, in order to minimize the likelihood of ground loop issues. With balanced (xlr) interconnects, this is unlikely to be an issue.
Obviously there are many other variables that enter into the picture with respect to speaker cables and power cords.
Keep in mind, also, that "more important" does not necessarily mean that a more expensive cable will be better at that location. For instance, some very expensive interconnects have high capacitance, which is a poor match for components with high output impedance.
Good luck!
-- Al